The NC was never a separate character.
Sometimes that line is valid. The AVGN, the Cinema Snob, and Plinkett are all examples of guys who are both Internet critics and separate characters. But most of the time, it's just a line people throw out to attempt keeping their audience from taking things too personally, and allow plausible deniability when they talk about how much they'd like to rape Hope Chapman.
Doug isn't even kind of an actor. He "plays" the same character every time: a screechy, unstable, hair-trigger, nerdy sociopath. Go back and look at his stuff. Is there really any significant difference between Doug and the Critic? Hell, even Melvin, brother of the Joker and Chester A. Bum? It's the same fucking routine every time.