1926 is the date Amelia Bones gives for what she suspects to be Quirrell's true identity. It is also the date of Tom Marvolo Riddle's birth in canon. This and other details suggest that Bones believes Quirrell is Riddle. But for that to be true, it must be that during Voldemort's first campaign, Riddle was still appearing as Riddle until, apparently, 1973

Bones must not know Riddle is Voldemort, or she would be behaving very differently towards Dumbledore. Dumbledore, on the other hand, appears to believe Riddle is Voldemort, because just a few chapters ago he told the Marauder's Map to find Tom Riddle when he was looking for Voldemort. Therefore Dumbledore must not know Quirrell is Riddle. It's maddening how many problems could be solved here by the characters' sharing information with each other.

Anyway, given that Riddle is Bones' hero, much of what Riddle told Hermione may have been perfectly truthful. And here is what especially caught my eye:

I stopped trying to be a hero, and went off to do something else I found more pleasant.

So it sounds like Riddle initially created Voldemort so he could make himself into a hero, but then decided to be Voldemort full-time, because it would be more fun. This he did for eight years, from 1973-1981.

Similarly, Riddle previously told Harry (in chapters nineteen and twenty) that he decided not to become a Dark Lord, and that he realized that if he did everything necessary to do that Dark Lord gig right, there would be no point. What if he was telling the truth? What if Riddle decided to dispose of the Voldemort persona because it stopped being fun?

Personally, the thought of someone totally amoral and willing to totally change around their plans based on what is most fun is rather frightening.

EDIT: See also this comment of mine, which lays out the story I am proposing in chronological order. Note that my confidence in what Riddle was originally planning on doing when he first went full-time as Voldemort, and my confidence in his motives for abandoning the Voldemort persona, is lower than my confidence in the rest of my theory.

quid quid latine dictum sit, altum videtur?

Nitpick: "quidquid" meaning whatever is one word not two words. While ancient Latin didn't have spacing between words, we can see that in this sort of context it was intended as a single word because Latin allows a lot of word order rearrangement and "quidquid" didn't get split up (as I understand that). "Quid" means "what" but "quidquid" means "whatever" or "anything".

And there's a disclaimer necessary here that I haven't taken Latin in a decade so I could be wrong but I don't think I am.

Thanks! Here for comparison is Google's translation:

Non habet soter salvator.
Vindex est dominus no,
nec mater nec pater,
modo nihil est.

If "Soter" or "Sotehr" means "savior", as I seem to recall from Aristoi, that might suit the meaning well; and if the first line makes sense grammatically, of which no clue hath I, it has a good ring. "Defensori" does sound closer to the intended meaning than "victori" or "vindex". And whether "modo nihil est" means at all the same thing as "modo nihilitas supera", I've likewise no clue but it sounds like the "above" part was left out. If it actually does convey the same meaning, it is more compact.

If this version works, it would have a powerful ring to it:

Non habet soter salvator.
Neque defensori dominus,
nec pater, nec mater,
modo nihil est.

But one suspects that what's actually needed is:

Non est salvatori salvator.
Neque defensori dominus,
nec pater, nec mater,
modo nihilitas supera.

LATIN REQUEST: I need a spell that Dumbledore uses to summon the Sorting Hat. So far, Google Translate on "Attend, Sorter!" got me "Adtendite Ordinarium!" but I'll take other appropriate phrases if they've got better translations.

pileum dictionis, affluere!

It would make Vergilius turn over in his grave, but it roughly means "(felt)hat (of the) talking, flow (to me) (i.e. appear)"

took the liberty to base it on the german translation of the sorting hat, which is "talking hat"

Edit: Adtendite Ordinarium means something like "mind the order". google really sucks at latin ;)