I wondered the same thing, But couldn't he also later use the stone to reverse it by re-transfiguring it to Voldemort's body?
You can't transfigure (via free transfiguration) anything into a target you don't understand completely. Otherwise it will be just an imitation.
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 118.
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.)