Well, don't expect this to be an in-depth point-by-point analysis of pony society or whatever. It's just a bunch of things that have to do with basic manners.
Where to start...? The end? Rear end, to be specific.
Pulling tails, surprisingly less rude than what you'd think, given that ponies lack certain standard parts that humans use to grab one another's attention (literally or otherwise). Unless the pony has been previously... stimulated... then it's private, but then again, that would only happen in private. Still rude between strangers, unsurprisingly.
Nuzzling, sign of affection, kind of like a small hug. Speaking of which - neck hugs, like those Celestia likes to give Twilight and Luna, are a hug of a stronger context and a sign you really appreciate one another. Hugs with both forelegs are used on highly emotive situations, since you are taking off your support to replace it with another's - meaningful, right? Human-me can get away with using both arms to hug all the time, given my biped nature freeing my limbs - and ponies love me for it. (After they stopped screaming, but that's the flower trio for you.)
Wings! A little similar to hands - holding a wing and not having the pegasus punch your lights out is a sign that the pony likes/trusts you, since those are sensitive (ask Dusty Feather, or better yet, Ditzy Doo - I can hear her from my Ponyville room on certain nights if I don't use the enchantments). Preening or otherwise grooming a wing that doesn't belong to you is something that either professionals or close friends (and 'up') do - unless the owner busted something or botched a landing and you're helping, then it's like dusting off hands and hair (embarrassing if said pegasus isn't that out of it). Certain spots, like in between the wings, are... sensitive, however, and should be left alone unless the pegasus says it's OK.
Changeling wings are ticklish and deliciously crunchy and squishy to the touch. Hyacinth and Black Lotus... well, let's leave changelings for later.
Horns? Well, having it filed feels like a massage. I have my ridiculously humongous chaos powers to thank for the opportunity of experiencing that- I convince the universe that I am a pony, you see, and while this means I don't technically need actual unicorn magic to do the same things, the feeling and ways of control are mildly different between the two.
Hmm... oh, right! If the horn is channeling magic, it becomes more sensitive. For context, hands work once more. Sweetie Belle slapping Rarity's horn is just like slapping someone's hands; mildly rude, but usually completely justified.
Of course, a powerful, complex spell will likely explode on caster and interrupter; mine only blow up my enemies, though, even if it was an ally who interrupted me.
Yes, you can use a horn in that context - in private of course; unless you've got some serious courage and confidence in your stealth spells.
Otherwise? It's just like a hand. There is horn fencing, where contact doesn't mean anything more than someone throwing a punch and the opponent catching it with their hands. Oh! There is a variation of jousting, where the participants charge at one another and use their horns to try and rip away a flag/cloak hybrid hanging from the opponent's shoulder to score points; naturally they use armor.
Pulling somepony's horn is like pulling their hair, though... only much more stupid, since even semi-experienced fencing unicorns know a way or two to turn their horns into a less friendly surface, even through the uncomfortable feeling. Or they could just channel raw power and blast you off - if the heat of the power doesn't hurt the grasping appendage, that is.
Related to the advantage of hands; I have two, so I can theoretically divide the strain and effort to cast much more complex spells than I should be able to cast if I where a regular unicorn of the same level with a sole horn, as if it were juggling with both hands instead of just one (the Alicorn Amulet does this in addition to the power boost, explaining why high-end spells could be cast like that); the disadvantage being that hands are nowhere near as resistant to the strain of casting and using too much power will burn them (be it in a single spell or repeated castings without resting time, it's the reason Twilight's horn sizzled on occasion). In practice, though, not only does my staff takes off a lot of the abuse, but the dragon magic within makes me largely immune to the heat I produce (still awkward, though), and the other two pony magic aspects divide the strain and effort through my whole body and boost my resistances further - hence the reason I can cast the higher-end chimeric spells I developed, which are rather demanding, without even injuring myself.
Still managed to statue-ify myself from the soreness and feeling of electricity coursing through my body. Couldn't let the others know I had chaos magic, so I had to suppress it severely.
At least I struck a pose beforehand, so the audience was none the wiser.
Back to ponies. Poking things with horns, a sign of impatience. Or that you are minutes away from blasting the offending target with a spell.
Suppressors for magic do exist, capable of cutting off the magic of all but the most powerful and skilled of casters, but their use is super-outlawed unless we are dealing with a magical malady that puts the pony in danger (either by loss of control over their magic or whatever), a mental breakdown that threatens the same, or the most heinous of criminals. Due to the mix of dragon and dark magic I have, they don't quite work on me; they melt off from the inside out. I have been forced to do something even worse - doing like Discord and taking away the traits of the other pony, but I just couldn't risk them knowing a suicide spell. Some of you might like to hear that story, or, if you are like me, feel like I should have knocked them through a wall first.
Fully egalitarian society - being a colt is just the same as being a filly. Only that one of the genders has a wee bit more social pressure and higher standards than the other due to the skewed gender ratio, which is the reason the 'gentlecolt' and 'lady' descriptors exist (an attempt to be seen as 'desirable' by the other side, while also making them feel useful). This Equestria is only matriarchal in the sense that the highest authorities are female and, as long as the universe follows canon semi-closely, the very idea of a gender-inverted social paradigm is ludicrous. What else...? Titles and stuff are inherited from both parents -though ponies tend to ignore the lesser rank- and the only times a distinction between male and female heirs is made are either by the nature of the inheritance (mom can't give her colt her wedding dress to use, unless he's in one of those relationships) or by family tradition (Grandma made the estate, gives to first-born daughter, who gives to daughter, etc...).
Opening the door for a lady, for example, is a remnant of the times things were... difficult. It's the stallion's duty to make sure his family is safe, and opening the door to the shelter to make sure everypony is accounted for was just part of it. (The other being to make sure that whatever pursuing monsters leave you alone, hence fencing and jousting).
Same-sex attraction... no-one cares. Well, seeing a stallion who only likes other stallions (or the gender-inverse) is unusual, but you won't be given grief over it should you be in a situation like that. Other than rude comments and frowns from a pony here and there, anyways.
Changelings respect all kinds of love, and you do not want to make enemies with a race full of of seducers, illusionists, manipulators, mind-benders, and shapeshifters with an innate notice-it-not field around them and other sneaky things. These guys are natural ninjas, and I'm taking full advantage of it. Luna has her bat-wing spell, Celestia has her polished golden armor, I have the discretion part (which is odd, since I already said I am bad at it... but then again, I don't need to be good if I'm employing others who are, both by cutie mark or by it being hard-wired onto their bodies).
That and Celestia passed a law saying that you can't ignore the established laws just because a mare doesn't like stallions or the reverse. You break a window or spout hate-propaganda, you get stomped by the long hoof of the law. And ponies will come down on you hard! That thing is like... three hundred years old! You should know better than that.
Herds... eeyup. A guy (or two) can have multiple mares. 'Regular' couples like the Cakes are common, though 'sharing' does exist. Word of advice - dating multiple ponies the same day is still going to make you two-timing, cheating scum unless that's the arrangement between all of the involved, or you are a victim of the circumstances. And since it's an egalitarian society, mares can be scum too, and can be frowned upon just as much as the guys - not to say that somepony can't weasel out of it, particularly if they are as 'resourceful' as Rarity or Big Macintosh (not to say that those two get into those sorts of trouble, but certain... characters with similar traits do).
I had to steer the conversation to keep Twilight from giving me the unabridged version, but I think I did OK. Well, I added my own commentary just now, but I think it's easy to differentiate between what Twilight told me then and what I added now.
"I appreciate the effort you are making." Twilight said after one of my many comments, while we walked through the street that... Carousel... darn. I was really out of it! Containing the desire or pranks was easy as long as she was talking, but by then, I just wanted to do something random!
I took a small chance to act my role. I walked around a puddle of mud left from a pegasus losing control of their cloud, and carefully extended a wing over it, leaning down and to the side to facilitate the climb.
"Oh my, so chivalrous!" Twilight said, giggling into her hoof.
She took a step onto my wing, rock-solid pinions unyielding under her weight, while simultaneously experiencing great softness under her hooves. The muscles tensed to hold her, pegasus and earth pony traits working together to do so without so much as a twitch, while keeping the wing and its feathers like silk to the touch.
I like my wings.
"Wow, like granite wrapped in a cloud, like the princess's." She commented in a whisper, stepping over the mud with a lady's grace. She turned around and gave me a curtsy in a jab at my behavior.
Let's see... maybe I can get some insight on what was going through her head. Excuse me if things go... wonky; I try not to do this too often. *AHEM*
Meanwhile, inside Carousel Boutique.
Oh, hey, it still works.
Rarity was working on a few sketches, most of them for dresses, but a few of them were reproductions of the outfits I had shown them the other day with the stories, as well as new ones based on those. Some were for humans, others were ponified versions.
"Hmm... I must admit these outfits are quite..." She trailed off as she inspected a sketch for a pony-version of a Red Mage's outfit from Final Fantasy. The pony in question looked adventurous with that feathered hat and a cape, with a cravat and other fashionable accessories. Her eyes fluttered as she sighed, no doubt imagining a handsome stallion wearing that, or the 'simplified' version which is a red cloak and the signature hat.
"Oh my!" She said in whispers, bowing and offering her hoof at an imaginary stallion. Ha! Called it!
The clock was ticking quite loudly, or so it seemed, because each one of the repetitive sounds made her smile fade bit by bit. Once it was gone, the sheer boredom she felt was evident. Her eyes began to dance around, her imagination taking her far away from her work once more.
"These days have been... interesting." She mumbled. "I just wish I had somepony to share them... outside of my friends anyways."
She walked over to the window aaaand...
Oops.
She swept the street with her eyes, which came to a stop upon a familiar lavender pony... and her companion.
Her eyes opened wide, all the better to see with. A stallion with a coat between raw umber and soft soil brown, with a deep dark mane that flowed in the gentle winds behind a long, fluted horn.
"Oh my stars!" She breathed the words as her eyes followed down to the wing that extended to prevent the librarian from walking into a puddle. The feathers shone under the sun like polished wood while they offered safe passage to the pony on the other side.
"A-a-a-a- royal blood?! And what a gentlecolt!" She covered her mouth with a hoof as Twilight did the same and tittered behind hers.
She stared, mesmerized, as I helped Twilight across without a hint of movement. Oh God, she's ogl- oh, that's just my left cutie mark.
"A circle of some sort? A cutie mark in magic..." Her brows knitted as she tried to construct a scenario in her head, while watching as her friend politely bowed. "She must have met him in Canterlot... but how did she get here so quickly? Didn't Princess Celestia nor Aether need her after all? Did he have something to do with this?!"
She had no idea.
Also, those eyes of hers are like a pegasus's, if she saw my mark.
She kept watching as we shared a small laugh, though she couldn't hear us through her window. She brought a hoof to her heart, nearly swooning at my apparently polite conduct (Twilight had just then jokingly said that '(I) might just make prince one day'). Then she suddenly righted herself, tense with determination, the fire of her will shining behind her eyes.
"The opportunity has presented itself!" She called to no-one in particular. "I simply must not let a stallion like that escape from between my hooves without doing anything!"
She saw as Applejack approached us.
"I have no time to waste!" She turned to her papers, flared her horn, and magically started up the nearest sewing machine.
I think I've seen enough.
Back outside.
"Howdy, Twi!" Applejack greeted us. "Who's yer-..."
She trailed off as she stared at my eyes, raising an eyebrow; I prevented Twilight from saying anything by extending a wing. Applejack can't catch a lie for peanuts - that 'living lie detector' ability she's given so often is a complete fabrication, else the 'MMMMystery on the Friendship Express' would have been over in a snap- but she can tell a trustworthy pony from a 'no-good two-faced snake' and it's hard to lie to her - to her face at least.
Also, her eyes are pretty, even when she's confused. Well, my eyes are still dark brown, which isn't very common here, which contributed to the look of half-recognition she was giving me.
"How is Macintosh doing after our encounter?" I said, giving her the last clue and making her gasp.
"Aether?" She asked, and I nodded.
"Prince Aether." I said, rolling my eyes. "Apparently both princesses decided that I should be tossed to the ravenous wolves known as 'aristocracy' instead of being made a professor of science."
Oh, and no, I don't get a coronation. Didn't quite earn it in that sense, you know? I'm more like Blueblood than... well, you should know by now. I get an office and responsibilities, not an estate. Blueblood does have a lot of lands, but those are inheritance. Not to say that I don't have a house that is one-hundred percent my own, but that's a gift for human-me in exchange for my/his services.
"Well, if'in yah need chaos ta live, Ah recon yah won't find a better place to raise as much of a ruckus as yah want." She said, chuckling.
"Why, Lady Jacqueline! " I said in mock horror, and she gave me a funny look half-upset half-knowing. "Are you suggesting I abuse my position and powers to whip those uncouth, dishonest, cheating ponies into shape using a long series of pranks, political movements and amateurish psychological maneuvers?"
"Y'all don't hafta be so formal, yah know?" She said, funny look still in place. "And yes, that there be exactly what Ah'm gettin' at."
"I am a prince, I have to treat a lady as such." I bowed.
"Shoot, Ah ain't no lady." She blushed slightly, turning away from me. "No need to treat me all special-like."
Rarity opened her window about then, intently observing us, which means that she could listen to what I said next...
"On the contrary!" I said, standing tall and proud like when I was presented, raising my voice slightly since there were only seven ponies in all of the town that could see or hear us and I was talking to two of them. "Within every mare lies a goddess, within every stallion, a god, and they must be treated with the respect and adoration they thusly deserve!"
Rarity, hearts in her eyes, fainted at that. Huh, explains why she couldn't hear Twilight laughing after a beat or two.
"You're dying to prank somepony, aren't you?"
"You know me too well, Twilight." I replied. "But that'll come later."
I turned to Applejack. "My form changes my behavior a little, so I act formal unless I consciously think against it."
She makes a little, adorable face of comprehension. I still wasn't done with her, and I wanted to see if a few fanfics applied to this universe, what with me having altered at least one significant point in the timeline.
"Better get used to it, my sweet little Tangerine." I said in a playful tone.
I swear I heard the moment her brain broke. She just stood there, a blank look in her eyes.
"Uh... what didya call me?" She asked after thirty seconds, by that time Twilight was a little worried at the plastic smile Applejack had.
"Well, you are related to the Manehattan Oranges, right?" I asked as innocently as the cat that ate the canary. "And with your coat color, I thought that I'd like to be more original with my nicknames than going the obvious route of apple- or farm-related names."
She let out an uneasy laugh, smiling rather forcefully and looking everywhere. "Oh..."
I leaned towards her and whispered to her ear. "Well, your secret is safe. Who knows? We might have fun together in Manehattan."
"How didya-?"
"The magic of imagination." I said, straightening and smiling at Twilight. "Now come on! We might be invisible to others, but that doesn't mean I want them to bump into me."
We continued our small tour of Ponyville, Twilight giving Applejack a brief summary of the story. The farm mare wasn't too happy with the deception, but conceded the point of the action being necessary. A human prince? In this world?
And the itch of the pranks was getting a little awkward. It didn't help that Dash saw us and flew towards us, adding her to the troupe of invisible ponies.
For the account of the stunts I pulled, I think it's better to wait until next time.
Oh, and Rarity. Sweet mercy did she give me a scare!