I'm not sure why almost everyone assumes that the first and the second H&C is the same person. Is there any reason to think so, beside their appearance?
Same appearance is a clue to the two H&C-s being related, but not necessarily to identity. For example, a hat and a cloak may be a uniform in a secret society, to be worn in special circumstances. Or, maybe two of them were friends and did pranks like that in their youth. Or, one of them saw the other do this trick once long ago, was impressed, and remembered it. Etc etc.
What I'm leading to is the possibility of the first H&C being Quirrell, and the second being Lucius.
I think Eliezer referred to both of them as "Mr. Hat-and-Cloak" in the author's notes.
(The HPMOR discussion thread after this one is here.)
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. There haven't been any chapters recently, but it looks like there are a bunch in the pipeline and the old thread is nearing 700 comments. The latest chapter as of 7th March 2012 is Ch. 77.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
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: