A useful thing to add would be ability to change who you’ve replied to. Either to a different person, or if you want the reply to be just “to” the whole thread, ability to remove the name.
Like in this case, I started writing a specific reply, then after I posted I realised it would have been better as a reply to the whole thread, but no way to change (as far as I could see at least, please advise if I’m just unaware of method).