Personally, I don't respond at all to PMs from people I do not recognize from their postings in the forums. Nor do I initiate PMs with same. However, I do try to thank people for gallery comments (once I see them, I am not often in the galleries)
I don't think all of the women here don't "want" PMs, I think we want respectful and intelligent PMs, from people who have taken the time to read posts and profiles, if we are going to respond to them. We have discussed many times our distaste for the receipt of the "group" PM; the one that goes out to most of the women (and the names are clearly displayed in our message headers) that contains invitations to cam or 'rate a cock'. Afik, none of us respond positively, if at all.
I do PM with people I have become familiar with, sometimes there isn't an appropriate place to put the message in a thread.
I also PM people when I find something or 'some things' they have posted worthy of positive feedback or comments. I don't think we as a society spread enough positive karma , so I try to do so, cos I believe people need to receive good vibes.