why don't Harry and Quirrell cast Somnium on Bellatrix instead of deceiving her? (The deception requires Quirrell to tell Harry the Death Eater password, among other things...) Why does Quirrell talk to Bahry so confidently while Bellatrix can hear him? Why does he follow his whims to play-duel and then kill Bahry instead of quickly subduing and memory-charming him, if they planned to pull off the perfect crime?
That reminds me of something else Quirrell arranged for Harry -- occlumency. If they read Bella's and the Auror's mind, they'll see Harry as a villain, and since Harry has training in occlumency, he's no way to prove them wrong. The entire thing looks like a set-up.
Harry didn't even consciously try to stop Quirrel's killing curse. It was an accident. Quirrel couldn't have counted on it happening to set Harry up.
[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.