If the headsets are hardwired, the SM can set the tone for how they're to be used. However, if walkies are used in the US, the FCC regulates profanity (strange but true). Should profanity be overheard because you're being monitored or accidentally overheard or something, you can get fined.
Personally, I've had people miss Qs because they were so busy gabbing over headsets. I don't mind a little chatter, but once the word "Warn" is spoken I insist on radio silence until I hear "Complete." And, if people start getting carried away I'll ask them to calm down. Because one never knows who is listening in, I do ask that there be no profanity and that the airwaves not be used to make fun of others. That can be done over a drink after the show.