Can't this be solved by having conductor Harry pass his Time-Turner to smelly Harry around 5:30 PM? Then none of the in-between Potters actually have Time-Turners.
I don't think so; he needs to use it himself at 6pm to transport everyone back, and smelly Harry mustn't go back himself. [EDITED to add: oops, I'm a twit; it looks like this works. So if this hack isn't viable in the MoRverse, it must be for some other reason, perhaps one of the ones below.]
My brain's fuzzy enough that I'm not confident there isn't some patch along those lines, though; if it turns out that there is, an alternative (which I can't rule out being already refuted by something in canon or HPMOR that I've forgotten) would be that a Time-Turner ...
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: