Similarly, when I notice someone writes a lot of interesting comments, I'll skim their user info page. If I find a note asking me to avoid certain subjects in comments, I won't put them on my reading list.
It's not that I object strenuously to being told what I'm allowed to say or do. (I am married, after all.) It's that two months from now I'll have forgotten that I'm never to talk about dental care, Flaubert, or male pattern baldness in that person's presence, and I don't want to make a faux pas.