John Mulaney also dropped Dave Becky, the manager villain of the Louis CK story, switching to someone else at 3 Arts. Other than Pamela Adlon, he's (AFAIK) the only high-profile comedian to do so. (Please do tell me if I'm wrong! Maybe there was a VERY QUIET exodus I didn't see.)
When you tell your grandchildren about this day, remember to explain to them that John Mulaney was first.