Huh, I missed that. I thought it was EY's way of dropping in a cultural tidbit about the wizarding world, where a transsexual girl is naturally thought of by everyone as a girl, though they all know that she makes her body the way it is by being a metamorphmagus, and she reverts to her non-metamorphed form when she's startled. Then I started wondering what non-metamorphmagus trans people would do. Maybe there are permanent sex-change potions. Or perhaps temporary ones that you have to keep taking, like polyjuice but without copying anyone. Or maybe all trans wizards are metamorphmagi, but I doubt it.
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: