Oh yes, that's why I said it was so obvious as to surely not be the answer. The problem with the Faceless Man for me was that you don't obscure your face without a very specific reason. And in books that reason is usually that we already know who this person is. But there just really weren't that many viable options of characters we had met who could plausibly also be Faceless. So David Mellenby popped right out on that short list. Of course [extended redacted Hanging Tree commentary about the Faceless Man and facelessness in these books as a thematic statement] so there's that.