He was sort of surprised! I mentioned that they probably wouldn't come back as the same person as before—he takes their souls, souls are the essence of people, you know how it is!—and he said something sort of interesting!

[ ...yeah why not, she'll tell Inigo. ]

He said that souls are actually pretty malleable, and if you mess with them enough, you could make people into blank slates, too. He doesn't know how to do it himself though, so I think everyone's safe.