What's more, Quirrell is a master legilimens; if he's willing to pull off a Groundhog Day attack on her he might as well just read her mind and get it right the first try. There's no point in wasting time, magic, and risk of getting caught when you could just do the job perfectly in 30 seconds.
Having one's mind read for the first time seems to leave some kind of trace; if he's not sure she's ever had her mind read before he shouldn't try it because then Dumbledore or Snape could learn later that someone's been peeking.
This seems to be borne out by the events of Chapter 79:
Albus said heavily, "A person who looked like Madam McJorgenson told us that a single Legilimens had lightly touched Miss Granger's mind some months ago. That is from January, Harry, when I communicated with Miss Granger about the matter of a certain Dementor."
Even if Hat and Cloak is Quirrell, the job had to be done the hard way, without Legilimency.
(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: