Assuming it's her arm, which is plausible given that Harry noticed its thinness but isn't confirmed. In any case, I was mainly just raising the question.
It's also the only explanation we have for Voldemort's assertion in 108 (I think) that he has further use for "her, or rather a certain part of her".
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 117.
Plans for next chapter release:
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)