Regarding singing along with Joan Baez, chances are, she had a PA system and monitors. I've yet to play in a session where these are provided. There have been a few players at sessions in recent memory, where I'd have taken this or that player out of my monitor mix, had it been an option.

I'm getting ready to head home from a visit to Chicago. While here, I played a a number of sessions, a couple of which I've played before. There was one that was absolutely remarkable last year, before people found out about it. After about a half hour of it this year, I found myself staying only out of courtesy to the session host who'd invited me. It's really sunk. It only takes one or two loud players playing out of time to tank an otherwise good session.
I play the instrument that most people find it easy to be unfriendly to, and barring being introduced by a regular, I often get a few looks until people see that I'm not "one of those bodhrán-owners" and that I can play quietly in time, and trade off with other percussionists. I can't say I blame the regulars of a given session for not throwing down the red carpet. Chances are they've been stung by being too friendly before.

Rich