Time to play "Avoiding Bat-Deduction"! · 4:08am Jan 18th, 2017
Bat Deduction, for those who don't know, is the name TVTropes has given for instances where a character makes a crazy leap of logic, but still manages to reach the correct conclusion. It tended to get used a lot in the '60s Batman series, hence the name. I've been guilty of it myself in my works - not here, but elsewhere, and not in serious quantities. And I've tried my best to avoid it in the Quiververse proper. Don't make more assumptions than you need to is good advice in general, after all.
That said, I think it's a good idea to lay out the facts, both to make sure that there isn't faulty logic in there and to summarize everything that's relevant as far as who knows what regarding Sunset Shimmer and her origins.
Item One - Everyone at Canterlot High knows about what went down at the Fall Formal, either because they experienced it first-hand or because they heard about it from people who were there. They know about magic, they know about the portal, and they know about Equestria, but with the exception of a few, they don't know complete details.
Item Two - Principal Celestia and Vice Principal Luna know the complete truth about Equestria and Sunset's origins. They had three friends who attended CHS with them years ago - Zecora, Radiant Hope, and a third individual who is thus far unnamed (but I've left enough clues and hints that people should be able to make an educated guess). The two of those three who have appeared thus far are aware of Sunset and her origins; whether the third is aware or unaware is currently unknown to everyone.
Item Three - Sunset Shimmer is aware of what Principal Celestia and Vice Principal Luna know, and has shared this information with her immediate friends. Currently, this consists of the Rainbooms, the Crusaders, and Flash Sentry. They're also aware of Zecora, Radiant Hope and the unnamed third CHS alumna.
Item Four - Zecora runs a shop, and has three employees; Sunset Shimmer, Lyra Heartstrings, and Sweetie Drops/Bon-Bon. Lyra and Bon-Bon have greater knowledge of Equestria and its magic than the rest of the CHS student body as a result of being employed there. They currently do not know how Sunset has knowledge of Equestria and its magic, but they have two theories - that Sunset gained her information from someone else with access to knowledge of Equestria, or that Sunset is from Equestria. Based on the information they have, the former is most likely (though the latter is the correct one). Sunset, similarly, is aware of the possibility that they know about her, but has no firm evidence and isn't going to press them on it unless she needs to.
Item Five - Members of the CHS faculty know varying levels of the truth regarding Sunset and Equestria - some know the complete truth (Granny Smith and Cheerilee), some know partial truth (Cranky Doodle), and others are currently unknown (Miss Harshwhinny). Whether or not this changes is still up in the air, but Celestia's erring on the side of caution to protect Sunset.
Item Six - Outside of these people, the only ones who know anything conclusive about Equestria are Big McIntosh and Maud Pie. They were directly told by those in the know, and have no reason to reveal this information to others.
Item Seven - Doctor Time Turner, Amethyst Star and Roseluck weren't at the Fall Formal, and are picking things up second hand. They know about magic at the school and they know that Sunset is hiding something, but don't know about the portal or Equestria. And they have secrets of their own. They're at the school for reasons known only to them, and they aren't in a rush to reveal the truth.
Secrets aren't coming to light yet, of course, but they will by the time I'm done with my "Rainbow Rocks" adaptation. I just wanted to lay everything out and see if folks figured it made sense and everything flowed right.
Seems alright to me.
4387373 Huzzah! Solid logic!
Yes, this is about what I've gathered so far.
4387400 Good, I didn't miss anything.
So, various individuals have various amounts of accurate information, and everyone with complete information on various topics are keeping things relatively secret, but in theory someone could, in time, put everything together.
In short, the clues are out there, so someone putting them together off screen would not be any sort of stretch. No Bat-Logic required.
4387931 Dang right.