Since no one here has mentioned it (as far as I see), note that Harry spends a significant portion of chapter 91 checking his watch every two minutes. Also note the sentence beginning,
From the outside you would've just seen . . .
Given the frequency and the aforementioned sentence, I think it's not likely that he's just counting down the time till dinner. He could be distracting himself, but he keeps it up during the conversation with his parents. Also, HPJEV is presumably familiar with such a common method of distracting oneself when thinking painful thoughts.
For the record, my current bet is that he used his time-turner and some transfiguration to do something with Hermione's body. The first thing that comes to mind is partial transfiguration of her brain into something much more durable. Taking her entire body is also an option if he can work up a passable fake.
Also, note that chapters 88 and 89 are titled "Time pressure", and the exact date and time is specified repeatedly throughout the text. In addition, there’s something funny in chapter 90: Right before Harry has the hypothermia idea, there's a discontinuity:
...[The Headmaster] had vanished from where he was standing over the Weasley twins and come into existence beside Harry; George Weasley had discontinously teleported from where he was sitting to be kneeling next to his brother's side, and Fred was now lying straight with his eyes open and wincin
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: