Submitting to a venue when you are a member of the program committee
No is not frowned upon, at least in our field (TCS). I can provide numerous examples  for that. I saw it many times. PC members submit their papers, but they are handled of course by other members and, afaik, the whole process is not visible to them until the notification date.

Note that, some conferences (like IPCO) have strict rules. They explicitly say that no PC member shall submit a paper, alone or as a co-author. But if the Call for Papers does not mention, I guess a PC member is free to submit the paper.

What I have heard though is that even if a PC member submits a paper, it is claimed that higher standards apply to that paper (but I am not sure).