rot13ed because I am convinced I am correct and so this counts as a spoiler ;-)
It's pretty obvious to me that Santa Claus is fvevhf oynpx, nffhzvat gung "v'z abg frevbhf" zrnaf ur vfa'g va nmxnona.
Has this been discussed? It seems to fit, especially given the way things worked out in canon.
Ch. 61:
"Mr. Potter is an Occlumens? You gave him an invisibility cloak and he is immune to Veritaserum and he is friends with the Weasley twins? Albus, do you have any idea what you have unleashed upon this school?"
I can't believe we all glazed over this one. I only know because a TVTroper noticed in the thread. And Eliezer posted in that thread shortly thereafter and made no comment on it.
Yes, it's possible that McGonagall is just assuming, or that Dumbledore lied to her. But still.
Update: Discussion has moved on to a new thread.
After 61 chapters of Harry Potter and the Methods of Rationality and 5 discussion threads with over 500 comments each, HPMOR discussion has graduated from the main page and moved into the Less Wrong discussion section (which seems like a more appropriate location). You can post all of your insights, speculation, and, well, discussion about Eliezer Yudkowsky's Harry Potter fanfic here.
Previous threads are available under the harry_potter tag on the main page (or: one, two, three, four, five); this and future threads will be found under the discussion section tag (since there is a separate tag system for the discussion section). See also the author page for (almost) all things HPMOR, and AdeleneDawner's Author's Notes archive for one thing that the author page is missing.
As a reminder, it's useful to indicate at the start of your comment which chapter you are commenting on. Time passes but your comment stays the same.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: