The Joker: I took Gotham's white knight and I brought him down to our level. It wasn't hard. You see, madness, as you know, is like gravity. All it takes is a little push!
-- The Dark Knight
The narrative that we, the readers, are supposed to believe at this point goes like this: Hermione was given information during her little rendezvous with H+C, giving her some information that made her think that Snape and the Malfoys had it in for her, that the duel didn't happen, and H+C (presumably Quirrell) obliviated her memory of their first meeting afterwards.
Professor Quirrell has made numerous statements doubting Hermione's goodness. For example: "She is young, and to make a show of kindness costs her little." (60) Being Quirrell, he has most likely predicted Harry's sentiment on the matter: "But 3 out of 40 subjects had refused to participate all the way to the end. The Hermiones. They did exist, in the world, the people who wouldn't fire a Simple Strike Hex at a fellow student even if the Defense Professor ordered them to do it." (63)
I would like to advance the hypothesis that Hermione actually did attempt to kill Draco. Yes, she had been set up to stew in her paranoia and obsession over Snape and Malfoy by H+C. Yes, the memories of her meeting with H+C were obliviated. The idea of the blood cooling charm may have been fed to her. But in the end, she choose to cast it in anger on Draco (at least as much as you can choose something when an attacker controls the environment).
It appears to be in Quirrell's interest to dissuade Harry Potter from believing that there are good people in the world. Quirrell wishes Harry to learn that there are no good people in the world. What better way to accomplish this than giving Hermione, as the Joker would say, a little push!
I also find Severus' comments suspicious: "The appearance of insanity..." Severus murmured softly, as though he were speaking to himself. "Could it be natural? No, it is too disastrous to be pure accident; too convenient for someone, I have no doubt.[...]"
EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
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. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
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, ten.
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: