I have to agree with fezziwig that I notice that I'm confused about this idea that D writing in Lily's book somehow destroyed any hope of friendship between them. I don't understand your scenario: you think Lily was upset about the writing, blamed Snape, but never mentioned it, and that was enough to destroy a friendship? And Dumbledore somehow knew that writing in a book would cause this effect? "I want to destroy Snape's friendship... I know, I'll write in his friend's book!"
Given all the weird things that happen at Hogwarts, souls trapped in books and strange notes found under pillows and time travel, I kinda doubt Lily would stick to the hypothesis that it must be Snape, and never mention it.
EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
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.)
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.
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: