I just thought of something else, too, that could explain why it took so long if the duel were short.
Suppose Hermione won relatively quickly, at around 12:05. H&C obliviates and memory-charms her, taking as much time as the duel he makes her remember, which could be several minutes. Then he has to do the same to Draco. At this point, it's around 12:15 or so, and the memory of casting the BCC would make it more like 12:16. Then H&C casts the charm himself and realizes he doesn't recall what time it is exactly. Decides to go with 12:30 because overshooting is way better than undershooting here and he thinks he'll be safe with 12:30, especially if he doesn't have much time before he goes zombie or something and can't just check the clock.
(Anyone notice that Quirrellmort seems to be living Life: The Interesting Parts Version?)
The new thread, discussion 13, is here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With three chapters recently the previous thread has very quickly reached 1000 comments. The latest chapter as of 25th March 2012 is Ch 80.
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, eleven.
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: