It seems a bit much to call Dave Chappelle’s comedy “ground-breaking.” After all, Chappelle is no Lenny Bruce or Richard Pryor, and he lives and a works in an era when comedy has busted out of the world of grimy basement clubs and onto TV screens worldwide. Still, what Chappelle is doing with his profane and ridiculous show on Comedy Central is changing the face of the network, and for the first time, bringing black viewers to a channel usually considered the province of white college students, Jon Stewart fans, and aging stoners.