Just a piece, but one I haven't seen discussed- why has no one done a Priori Incantatem on Hermione's wand? We know harry knows about it, from clear back in chapter 13:
"Priori Incantatem," said Sprout. She frowned. "That's odd, your wand doesn't seem to have been used at all." Harry shrugged.
I don't know if this is part of Harry's plan, but it is certainly a line of investigation that has not been followed. There is always the possibility that whoever did the memory charm used Hermione's wand to cast the blood chilling hex, but once down that track Harry can start eliminating suspects for the memory charm.
And if her wand did it? Quite possible, but it wouldn't help.
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: