What gave away vampire Durkon to Roy?

[a_flemish_guy]

Or, alternatively, a Durkon who was willing to do that is no longer the same person that he once called Durkon. No longer the person who Durkon represented in his mind. (Same thing in the end, but it's a 'you "grew" out of being that person' as opposed to 'your body was hijacked'.)

yeah, it's like your best friend came over to your house, completely trashed it, ate all the food and drank all the drinks and then spit in your face, I'd bet that he wasn't the person who you made your best friend anymore

roy himself says it best on the next page: I don't know wether you started out as durkon and turned into this, or you're just squating in his corpse

it's less: "I now know the intrinsic mechanics of vampirism" and more "the durkon who I knew and considered my friend would never say such things and as such you must be somebody else"