That was originally where I was going with that, but further evidence of Harry's plan (the lack of any use of time-turning until at least six hours after the fact) has pretty well falsified my prediction.
Next easiest: Harry goes back 5 hours, sends a note to original Harry explaining exactly what he has to do to save Hermione; original Harry does the heroics, including setting up a fake death and writing the directions he got, while future Harry executes the actions in the chapter, failing to prevent the death. There's a maneuver somewhere in there where future Harry then snaps his fingers, goes back one hour, and somehow initiates the course of events described (probably by blackmailing time).
The theories have now gotten more unlikely than that Harry got the timey-wimey ball and is prohibited by an unstated rule from preventing a plot event.
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 90. The previous thread has passed 750 comments.
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: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18,19.
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: