Update: Discussion has moved on to a new thread.
The load more comments links are getting annoying (at least if you're not logged in), so it's time for a new Harry Potter and the Methods of Rationality discussion thread. We're also approaching the traditional 500-comment mark, but I think that hidden comments provide more appropriate joints to carve these threads at. So as of chapter 67, this is the place to share your thoughts about Eliezer Yudkowsky's Harry Potter fanfic.
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. The fanfiction.net author page is the central author-controlled HPMOR clearinghouse with links to the RSS feed, pdf version, TV Tropes pages, fan art, and more, 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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
Animate armor.
As Dumbledore demonstrates in Order of the Phoenix, any spell, even Avada Kadavra, can be blocked by a temporarily animate statue (the spell "kills" the statue instead). Which actually annoyed me when I read it, since that implies wizards could imbue each layer of their clothing with intelligence before a battle, and gain a bunch of extra lives.
(Having your breastplate shout taunts at your enemy also frees you up to focus on fighting.)
It wasn't the animatedness of the statue that made it block Avada Kedavra, it was that it was a huge block of solid stuff. Voldemort in the same sequence crafted a physical shield for himself, though he didn't need to block any Avada Kedavras (as Dumbledore didn't cast any).