The recent conversations Harry has with Dumbledore seem to imply that Harry is becoming what tvtropes calls a Knight Templar: a zealot who is willing to burn villages in order to save them. Such a person will very easily commit great evils in the name of "The Greater Good" (whatever that may be). I agree with Dumbledore on this. Harry has no brakes; he is willing to escalate his counterattacks without limit, collateral damage be damned. This may not technically count as "Dark" according to the dichotomy set up in the narrative, but it's still a completely evil way to act.
Update: Discussion has moved on to a new thread.
The hiatus is over with today's publication of chapter 73, and the previous thread is approaching the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: