(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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
Do you mean Eliezer said that in an author's comment or something? If so I concede the point, though the text of MoR doesn't appear to me to support the existence of either souls or afterlife (even ghosts are less sapient than they are in canon).
I'm also doubtful about it from a story-telling standpoint, since if spiritual immortality for humans exists by default, it would make all of Harry's stated ambitions to achieve transhuman immortality in the material universe, for everyone, a bit pointless and perhaps even restrictive (that's a whole new world you never get to explore, if you never die). Also, since MoR has a certain didactic function, for Eliezer to establish spiritual immortality in the Rationality!verse would kind of take away from the impact of his anti-death and pro-cryonics sentiments.
As regards your comment about Rowling, I think in canon there's at least one piece of evidence strongly supporting the existence of an afterlife. In Deathly Hallows, during the "King's Cross" scene when Harry is AK'd into Limbo by Voldemort, Harry ostensibly meets the departed soul of Dumbledore, who tells him all manner of things (regarding his own past and the Deathly Hallows) that only the true Dumbledore would know. If one is particularly skeptical, one can write this off as total delusion on Harry's part (thus rendering suspect everything "Dumbledore" tells him), but that would go completely against the spirit of the story.
V oryvrir ur zrnaf rivqrapr gung pna or bognvarq ol aba-qrnq crbcyr. Urer'f gur yvax.