I have never been "banned" from speaking to other Doms/Masters, but having a private chat is simply something I would never do. It just doesn't feel right. I believe it would be disrespectful to my Master.
I don't have any issues talking on open forums, or in open chat (if I were ever to have time to do such a thing again), but private chat is different.
I view it like this.... in real life, at a party, I wouldn't think it to be a problem to have a conversation with a Dom, or even a vanilla man, in a room with other people around. I do think it would be improper to go into a private area with him to have a chat on our own.
The exception would be, of course, friends who both Master and I know, and who's intentions are clear. But strangers/acquaintances? I just don't feel the need to engage in private conversation.
Just my opinion. Your mileage may vary.
-lily