I don't think the relevant category here is an incorporeal Patronus intercepting an Avada Kedavra spell, so much as it is Harry's magic coming into contact with Quirrell's. Which does seem like a possibility plausible enough to be worth considering.
Also, Harry has a history of interacting unusually with Avada Kedavra spells, which might lead one to predict an unusual interaction in this case as well.
That said, I expect a lot of that is hindsight bias.
Which does seem like a possibility plausible enough to be worth considering.
Quirrell put Harry on the steps, out of direct line of fire, so that Harry wouldn't try any magic to interfere with the duel or be hit by magic accidentally, and at this point he (rightfully) didn't know the Avada Kedavra could be intercepted or deflected by any magic, so he shouldn't have expected that Harry would be able to send any magic at all out into the line of fire of the spell.
I think it is mostly hindsight bias: before this particular event, nobody knew you could put ...
- 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.