(58)
Upon reflection, I still think Quirrell held the Idiot Ball in Chapter 54, by misjudging Harry's probable reaction to an AK attempt.
A big weakness in Quirrell's plan (assuming he wanted a successful prison break) was counting on Harry to maintain a stable Patronus. Harry is young, inexperienced at casting Patronus, and in a place liable to cause extreme emotional reactions, and he must maintain a Patronus strong enough to keep them hidden from Dementors but not so strong that it starts destroying Dementors or attracting attention.
The trouble started when Harry's escalating Patronus attracted the Aurors' attention, which was a foreseeable (and foreseen) risk. And it doesn't seem all that surprising that Harry's Patronus would go out when he saw Quirrell cast Avada Kedavra (although it is very surprising that it would block the spell).
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.