One theory I've had for a while:
Maybe the death needed to make a horocrux is not needed to preserve the mind. it is needed for the minds ability to cast independent magic. One could make a perfectly fine horocrux without killing anyone that had the only problem that you'd be a muggle when you were brought back.
This is the most important consequence of a more general theory: What a wizard means with the word "soul" is their independent magic power source, and that follows some conservation law. Evbidence for this includes wizards not considering mugles to be persons, and paintings appearing to have most of the information needed to completely reconstruct them in an easily readable form even if it can't be exceuted peroperly.
This would make Draco's statement that muggles don't have souls accurate. Combined with McGonagall's statement that AK strikes directly at the soul, it would seem to imply that (1) AK should have no effect on muggles, and (2) AK should be nonlethal, only rendering the wizard nonmagical.
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: