Which earlier mistakes were these?
The chief of them is the one that Harry realizes:
The part that was numb with grief and guilt took this opportunity to observe, speaking of obliviousness, that after events at Hogwarts had turned serious, they really really really REALLY should have reconsidered the decision made on First Thursday, at the behest of Professor McGonagall, not to tell Dumbledore about the sense of doom that Harry got around Professor Quirrell. It was true that Harry hadn't been sure who to trust, there was a long stretch where it had seemed plausible that Dumbledore was the bad guy and Professor Quirrell the heroic opposition, but...
Dumbledore would have realised.
I think Dumbledore did realize the fact that the Defense Professor is Voldemort, so that's no consequential error on Harry's part.
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 112.
There is 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.)
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: