Is 'Gravedigger' Sandor Clegane?

Gravedigger is a very large man and bigger than Brienne, he covers his face making it impossible for Brienne to identify him. He has a healing wound similar to that of Sandor's wound which he recieved at the Crossroads inn.

The Elder Brother of the monastery, while speaking to Brienne, seems to know an awful lot about the mind and soul of Sandor Clegane. Perhaps too much for having only briefly spoken to him as he died.

Furthermore, Sandor's horse Stranger is on the Quiet Isle, Stranger is violent towards any man who isn't Sandor so how would the priests be able to get Stranger along the Treacherous Path of Faith? The Elder brother who speaks to Brienne tells her that the 'Hound' is dead this could be because he is speaking metaphorically that the violent part of Sandor is dead but he is still actually alive. The Elder Brother is very vague while speaking of the death of The Hound. It is possible that that he believes the violent and angry version of Sandor has died and now the new Sandor lives on. This is supported by the fact that the Elder Brother mentions that he 'died' on the Trident when he used to be a warrior. In reality his 'death' only consisted of a major life change (as he believes Sandor has taken).