I'm not gonna duke it out with you guys over the merits of Waits' music--or his persona--but I will say I'm a big aficionado of his work and don't see him at all as a "fake" or pretender. Almost every performer takes on a persona of some kind, a mask, to both protect themselves from the pubic and present themselves to the public. Yes, Waits came from a middle class family and made himself (for a while anyway) into a street character and cheap motel dweller. Let's not forget that Bukowski came from a (lower) middle class family, not from the bowels of the ghetto, either.
In terms of a writer or perfomer being fake or a poser, I know what you guys are getting at. He may not have been a skid row dweller but when he writes and sings Tom Traubert's Blues, he's coming from a deep place of understanding and empathy. Nothing fake in that. Or Kentucky Avenue, that explores the wonder of childhood and the pain of disabiity and the way children perceive that in each other. Listen to Black Market Baby or Hold On and tell me he's faking it.
There's nothing inherently wrong with a mask or persona--if it doesn't get stuck to your face. I think that Waits knew the difference and eventually grew out of what he'd donned for a while. I think for Bukowski it got a little close but it made him very comfortable, financially, and he grew old with it gracefully, mostly. Where am I going with this? I say to my mirror that reflects the strongest and handsomest man in the village.