(The HPMOR discussion thread after this one is here.)
The previous thread is over 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 latest chapter as of 09/09/2011 is Ch. 77.
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, eight. 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Eliezer Yudkowsky which is not supposed to be publicly available (which includes public statements by Eliezer that have been retracted).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.
I have an idea for an epic maneuver that a wizard could perform as a last resort in certain emergency situations. A severely wounded wizard could, if there is something of much greater utility then his own life on the line, transfigure himself into a healthy version of himself in order to continue the fight. This would be a death sentence, but still worth it if the stakes were high enough.
Then again Harry can already sustain a small transfigured object even in his sleep. Perhaps the most powerful of wizards could sustain a transfiguration on their own body indefinitely. Or... Professor McGonagall said that it would be possible for a child to transfigure themselves into an adult bodily form. Perhaps if the wizard could not sustain an object the size of their own body indefinitely after the emergency situation has passed they could again transfigure themselves into a adolescent, child, or midget form in order to achieve a body with a volume that they could sustain. Unless doing another transfiguration would cause the consequences of the previous transfiguration to be imposed on the new form. Though I don't see why that would necessarily be the case.
This would be a very fragile sort of existence. They would be much weaker due to the constant drain on their magic and incapacitation or anything that dispels the transfiguration would result in death.
It's also been noted that trolls are constantly transfiguring themselves into themselves, which lays a pretty good precedent for this kind of transfiguration!