ETA: There is now a third thread, so send new comments there.
Since the first thread has exceeded 500 comments, it seems time for a new one, with Eliezer's just-posted Chapter 33 & 34 to kick things off.
From previous post:
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.
In canon, it was precisely Peter's fear (greater than that of his friends) which led him to join Voldemort. So while I wouldn't like to see Sirius made into a bad guy (since I side with wrongfully convicted prisoners and don't want them to turn out to be guilty after all), it would be a powerful statement in favour of the power to overcome one's fears if Peter stayed a good guy.
It would also be a powerful lesson if Peter was able to see when his loyalty to a certain 'side' was irrational and make a considered choice to do the action that best allowed him to achieve his own goals. But that is exactly the wrong kind of signal for Eliezer to convey! ;)