Yes, my theory definitely depends on believing that Quirrell COULD predict Harry's actions when he cast the killing curse on the auror. You also have to be willing to believe that Quirrell knew Harry would figure out a way to observe the battle, even though he was ostensibly lying out of sight. I think the first is more of a stretch than the second. Anyone who knows Harry at all could predict that he would try to find a way to spy on the battle: using the Patronus to block the Killing Curse is a much more specific action that only somebody who understands Harry really well would be able to predict. I guess I'm willing to believe that Quirrell does understand Harry that well.
Could Quirrell have guessed that Harry's patronus would block a killing curse? That seems like a stretch.
[Update: and now there's a fifth discussion thread, which you should probably use in preference to this one. Later update: and a sixth -- in the discussion section, which is where these threads are living for now on. Also: tag for HP threads in the main section, and tag for HP threads in the discussion section.]
The third discussion thread is above 500 comments now, just like the others, so it's time for a new one. Predecessors: one, two, three. For anyone who's been on Mars and doesn't know what this is about: it's Eliezer's remarkable Harry Potter fanfic.
Spoiler warning and helpful suggestion (copied from those in the earlier threads):
Spoiler Warning: this thread contains unrot13'd spoilers for Harry Potter and the Methods of Rationality up to the current chapter and for the original Harry Potter series. Please continue to use rot13 for spoilers to other works of fiction, or if you have insider knowledge of future chapters of Harry Potter and the Methods of Rationality.
A suggestion: mention at the top of your comment which chapter you're commenting on, or what chapter you're up to, so that people can understand the context of your comment even after more chapters have been posted. This can also help people avoid reading spoilers for a new chapter before they realize that there is a new chapter.