From S5E1&2 we got that all ponies affected had their particular talent reduced to below average: Pinkie became laconic, Rarity lost all sense of beauty, Rainbow became slower than the average, Applejack hurt herself trying to buck a door, Fluttershy lost all connection with animals and Twilight became nondescript. And the baker making those disgusting muffins, the tailor making those burlap capes... I wouldn't be surprised if the settlement had also included a former architect that now was unable to pile Legos, or a painter that was now unable to paint a house without a major mishap happening.
Pinkie's case became the most pronounced, as she became an limp balloon, being pulled down whenever she could muster any energy.

So, what would be your thoughts?

4252838
It clearly isn't just a removal of the magical aspect of the talent. If it were, the experience and physical conditioning would still be there. I think the equal marks have a sort of action/reaction connection: they push back against the talent every time a pony tries to use it, whether that use is magical (Fluttershy trying to talk to the bird,) mental (Rarity assessing the drapes,) physical (Dash flying,) or even behavioral (Applejack's inability to think of countryisms.)

Ironically, the reaction probably isn't equal to the action, but is locked in to prevent excellence of any kind. After all, the purpose of the equal mark is to make no pony better than any other, so it likely renders them all equally incompetent.

I consider it kind of a half-way measure of what Tirek did, with an added enchantment thrown in. When Tirek took away a pony's magic, their cutie mark went with it, but some measure of who they were still remained. Pinkie didn't turn into a depressive like she did here, for instance. What I think Starlight did is that she gutted the source of their magic, taking away as much as she could and leaving everyone with the bare minimum they needed to function. What she took was what we saw in those jars. This dampens the ponies' racial abilities and presumably also makes their cutie marks cease to manifest on their bodies.

Then the second part of the spell would be a suppressor of sorts, manifesting as the equal sign mark, which dealt with any elements of a pony's talent or personality that couldn't be removed by taking their magic away (e.g. a singer's voice, or an artist's creativity). A pony attempting to express their talent, as Pinkie did whenever she started getting too joyful, would activate the suppressor spell. This is what we were seeing whenever the equal sign marks did that pulse thing.

I'd also say that adding the equal sign mark is where Starlight sneaked in the brainwashing... but considering the scenes of the main six being locked in that house for days with propaganda blaring on loudspeakers, I'm not entirely sure that she didn't just do that part the old-fashioned way.

Well, for one thing, in "real life" I'm sure cutie marks would be something that it takes years to master the subtlety of, so if we want to conceive of Equestria as a real place for the purposes of fan works, we have to acknowledge that we're working from extremely incomplete information...

It always seemed to me that discovering your cutie mark was like finding a room in your house that you had no idea about. It was there all along, waiting to be unlocked, and overcoming the barrier to it, or finding the key, is the rite of passage that earns you a mark. But that doesn't mean that room can't be revamped or even excised and transplanted somewhere else.

If I had to hypothesize, I'd say the spell in Magical Mystery Cure exchanged those "rooms" among the Mane6, but because they didn't have any of the support structure in terms of personality, training, and intuition, those talents were unable to manifest. They had no fundamentals. Conversely, I think the spell in The Cutie Map re-closed the doors to those rooms, on top of suppressing even the "route" to them such that they couldn't be rediscovered—It was almost as if they were reverted to the status of blank-flanks, but the rout to rediscovering their marks was also blocked.

Anyway, that's my speculation from here on Earth, without the lifetime of experience with magic and marks that the "real" ponies we want to write about would have.

Note that what the Spell of Sameness does is not only to remove one's Cutie Mark, but also to block one's Talent. If one simply removed a Cutie Mark, but left the Talent intact, the moment that the Pony expressed and realized her Talent the Cutie Mark would re-appear, for the exact same reason it appeared in the first place. The equals-sign it generates is a Talent suppressor, possibly linked by the Law of Similarity to all the other equals-sign Marks to ensure that everypony bearing the Marks is reduced to and remains at the same Talentless lowest-common-denominator.

Also note that the SoS can't remove skill, only Talent. Rarity, for instance, knows how to appraise gems and sew clothing and run a business: these are skills she's gained by long application. Talent-suppressed Rarity can still do these things -- she just doesn't get the huge bonus (in a 3d6-based system I would rate it at around +5 to Skill for her incredible degree of Talent, with +1 to +3 being more common for normal Ponies) normally conveyed by her Talent. And her work would be merely routine and uninspired -- she'd no longer be able to match Talented competitors.

("Ah," says Starlight Glimmer, "but when all have been made equal, there will BE no unfairly-Talented competitors." Get thee behind me, vile spawn of Karl Marx!)

However, because a Pony is supposed to have a Talent, having one's Talent completely suppressed after one is not naturally supposed to be a blank-flank any more has worse effects. It also reduces (I'd say by about half) one's inherent racial magic. Thus, Earth Ponies suffer reductions to their telekinetic strength and toughness boosts, Unicorns to their manipulative telekinesis, and Pegasi to their flight-fields. (We haven't seen these used on other normal Kinds, but I imagine that Changelings would become less powerful empaths, and Sea Ponies slower in the Water). An Alicorn, such as Twilight Sparkle probably suffers reductions to all her combined racial abilities.

4253319
More than rooms, I imagine that a better fitting analogy would be to say ground level on a business-and-home building, or the programs running on a OS and hardware. If your business needs specific programs on its computers, and a given computer doesn't have them, then that computer is nothing but a paperweight. If a business-and-home building has the business shut down, then the ground level becomes little more than a source of depression and an encumbrance to get home.

Specifically thinking about the Cutie Mark swap, I would want to imagine the ponies as 2030 AI-driven cars (not a longshot, considering that we'll have car autopilot by next year or so). Imagine the girls as, say: Rainbow the roadster, Applejack the dented pickup truck, Rarity the limo, Pinkie the delivery van, and Fluttershy the ATV. After the swap they become the ATV-brained roadster, the limo-brained pickup, the roadster-brained limo, the pickup-brained delivery van and the delivery-van-brained ATV. Results? The roadster gets stuck in mud, the pickup tries to pickup a celebrity and the celebrity hails a cab, the limo rolls over as it tries to take a curve, the delivery van gets dented from the farmwork and simply doesn't have the oomph to haul stuff, and the deliveries never get done successfully between the ATV's rough suspension and tiny cargo capacity.

4253800
I would wish to mention that ponies were apparently still drawn to their own Talents, but these were suppressed to well below average. This is particularly telling with the pony that was later uncovered to have had a Talent for baking: she was still drawn to baking, but her skill was down to "less tasty than cardboard". That means that she was down to absolute novice, and couldn't get further up!

Uh... Makes me remember that, in 1937, the Hershey's Chocolate Company had been contracted by Uncle Sam to make an energy bar so unsavoury that people would only eat it in desperation. Thus was born, and mass produced, the D-Ration.