As a man, is it acceptable for me to wear black nail polish to work?
I'm a senior manager at a small-ish IT company in the South of Brazil. The company has no official dress code, and most people dress up very casually. This includes the board of directors.
While I wouldn't think twice before wearing a Mario T-shirt to the office, black nail polish is a bit more extreme than that. No other male employee wears nail polish of any sort, so I don't have any frame of reference for it.
There is no ban for nail polish on women, nor anything of the sort on beards, piercings and so on. I have waist-length hair myself, so that hasn't been an issue. One of the directors has a septum ring, so I would guess that's not an issue either.
The reason for wearing the black polish is to identify with my sub-culture and to prevent biting my nails.