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:
You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).
If there is evidence for X in MOR and/or canon then it's fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that "Eliezer said X is true" unless you use rot13.
"Beyond all panic and despair his mind began to search through every fact in its possession, recall everything it knew about Lucius Malfoy, about the Wizengamot, about the laws of magical Britain; his eyes looked at the rows of chairs, at every person and every thing within range of his vision, searching for any opportunity it could grasp -"
-and then the pieces fit together, and in retrospect it was obvious. The Boy Who Lived announced his discovery.
"I can deliver you Voldemort."
Harry knows enough to reasonably come to the correct conclusion about Quirrell's true identity, yet hasn't figured it out yet. If he's as deep into his dark side as he seems to be, and remembering everything he possibly can, I think he could realize the truth. Probably not going to happen for story purposes, but still a possibility.
It should also be pointed out, everyone thinks Voldemort is dead. Remember what happened in Order of the Phoenix to everyone who was spreading the bad news? That's more likely to be met by confusion than by bargaining.