It has to be Dumbledore, by Conservation of Narrative Detail: There's no way that the conditions of Harry's promise to Draco would have been spelled out in such detail if learning the truth would be all it took to expiate it.
It's going to turn out that Dumbledore did intentionally burn an innocent Narcissa Malfoy to death, but for a justifiable reason (though it's going to be interesting to see what that could be), and thus Harry is going to have the impossible task of convincing Draco to let him out of the promise.
Other than my desire for Snape to kill Dumbledore, I don't see any reason why HJPEV should talk Draco into letting him out of the promise.
It is more important to the themes of the work for HJPEV to follow through on a promise so dramatically given, than to shirk it. Likewise, it would be important for Dumbledore to face the consequences as administered by HJPEV.
You have an interesting point about the promise. It is awfully detailed for something that would just be set aside. Still, it could have been so detailed just to allow a semi-light character like...
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 81, which should be published later today. The previous thread passed 400 comments as of the time of this writing, so it will pass 500 comments soon after the next chapter is posted, if not before. I suggest refraining from commenting here until chapter 81 is posted; comment in the 12th thread until you read chapter 81. After chapter 81 is posted, I suggest all discussion of previous guesses be kept here, with links to comments in the previous thread.
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.) When posted, chapter 81 should appear here.
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, twelve.
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: