Re: Which one does ‘his’ indicate, Harry or Quirrell?
Given that both Harry and Quirrell could see the hand, it doesn't really matter, does it?
I've said many times that there are outstanding writers who don't necessarily tell a great story, and great story tellers whose writing ranges from very good to absolutely awful. It's rare to find both in one person. JK is a great story teller, and I find her writing most adequate to tell her stories. I loved every book and every movie.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.