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:
You do not need to rot13 anything about HP:MoR or the original Harry Potter series unless you are posting insider information from Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).
If there is evidence for X in MOR and/or canon then it's fine to post about X without rot13, even if you also have heard privately from Eliezer that X is true. But you should not post that "Eliezer said X is true" unless you use rot13.
She's not definitely called out as Tonks, and I'm not sure the years match up, but from chapter 29:
"Did you know there's a fourth-year girl in Hufflepuff who's a Metamorphmagus?" said Hermione as they headed toward the Great Hall. "She makes her hair really red, like stopsign red not Weasley red, and when she spilled hot tea on herself she turned into a black-haired boy until she got it under control again."
I've just decided to eliminate the "fourth-year" qualifier. I'd previously meant Ranma to be separate from Tonks, but on reflection it's kind of funnier if she is Ranma. More importantly, I want Metamorphmagi to be rarer and more unexpected than if two different ones are attending Hogwarts at the same time.