One of the things I like about him cutting off his face, in addition to how scary looking it makes him, is that it shows how fearless and unafraid of pain he is. Having your face cut off would be horrific, but he welcomed it. Most villains, including the very crazy ones, would be terrified of that happening to them. How do you hurt, scare or stop someone that is not even slightly scared of having their face cut off and the pain that comes with it. That wasn't the reason he had it done of course. I actually found the main reason he did it to be underwhelming. In regards to him catching Gordon out, it was a nice follow-up to DOTF where he said that he does be under there and hears Gordon talk, both when he is awake and when he is asleep. It is a creepy thought.