Barbara, in a setting such as the one you described, with all in attendance participants in the session, anything other than silence--or appropriate singing along--is unacceptable, I would think. Even whispered conversations between other people who are going to expect you to listen to them is disrespectful, not just to you, but to those listening. As for the creep loudly ordering dinner during your song, others in the group should have picked him up and tossed him out so he could place his order in the bar.

If the forty or fifty people attending the Irish sessions at the Starry Plough, many of them drunk, can (and do) maintain a respectful silence when soloists take over during the session band breaks, there is no excuse for less attention in a song circle. If the session has a leader, he or she should make that clear to everyone; if not, then a pause between songs might be time for a brief discussion of session ettiquette.

--seed