There were many interlocking pieces of evidence already pointing to the truth of Q == V (I think readers were actually chastising Harry for not figuring it out earlier at some point); the perfect timing of this particular incident was simply the part that happened to break Harry's voluntary suspension of disbelief enough for him to actually start trying to piece it all together.
As someone pointed out on Reddit, it's pretty suspicious that Harry figured everything out almost immediately after Snape hit him with a "Dispel Confusion".
New chapter!
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 104.
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: