There was speculation before Chapter 79, but H&C as anyone but a Hogwarts professor is killed by McGonagall's comment;
Obliviation cannot be detected by any known means, but only a Professor could have cast that spell upon a student without alarm from the Hogwarts wards.
There's some minor speculation that an ex-professor could have done it, and I suppose we could include Dumbledore and Lupin in the list, but Sirius and Grindelwald are ruled out (as of chapter 79).
Someone (sorry, I don't remember who) commented that the apparent sloppiness of the Ground Hog Day attack may be from the need to explain to the reader what's going on. It's also been pointed out that being a Legilimens doesn't guarantee competence in gaining trust, it just makes it easier to figure out that you haven't. As is typical, YMMV.
Much hay has been made of the line
and recognition sent a jolt of terrified adrenaline bursting through her.
With some claiming that it means Hermione both recognizes and is terrified of the real H&C. Others claimed that was reading too much into the prose, and the terror might just be from realizing the situation in general. Again, YMMV.
Current speculation seems to focus on the motive, as in, who would want Draco dead, and/or who would want Hermione accused of trying to kill Draco.
It seems likely to me that it will all become moot once chapter 81 is released, so get your speculations in quickly!
The new thread, discussion 13, is here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With three chapters recently the previous thread has very quickly reached 1000 comments. The latest chapter as of 25th March 2012 is Ch 80.
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, eleven.
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: