I am not because I live in a pretty conservative area. So I try to get some leftist points through to coworkers without opening myself up to the ridicule of just being a “commy degenerate” in their eyes. So I think I can get through to them better without outting myself as a Marxist.
It's an awful idea to let your boss know you're communist, wtf are you thinking?
In unrelated news my chuddy boss definitely knows I'm always communist because I can't keep my mouth shut, but for some reason he still really likes me (we bonded early on over boomer rock, I guess I do a good job at the company, etc) so hasn't been a problem yet