(The HPMOR discussion thread after this one is here.)
The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.
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. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
Indeed, when I sat down to make a rationalist MLP fanfic, I realized that the only part of the show that I would change is possibly Feeling Pinkie Keen.
Personally I've found a lot of the show's lessons to be overly one-sided and applause-lightish. Also, I like/dislike how the show dances around carnivory; I'd love to see HJPEV-Twilight (or whoever) react to Fluttershy explaining how she runs her meadow.
There's also the world mechanics of raising the sun and why only the princesses are immortal and all that, and various smaller mysteries, but (1) lots of fic writers and theorists are probably exploring that, and (2) a lot of it is high-profile enough in the series that it stands a reasonable chance of being elaborated on there. The fact that the Potter books have concluded is one of the advantages to setting a rationalist/munchkin fic there.