I understand what you refer to as clients. I have two types of clients - nonpaying and paying.
When I've dealt with beta projects myself in the past, inclusive of even my own, we've used a select amount of people to beta test the scripts (either by a beta test email list or by chosen who apply to beta test).
I'm still getting used to vbulletin's forums. I've never had a community where the beta and all was freely available to anyone. Of course, when I think about it, this is the first software (vbulletin) that I've had to pay for
I moved to vbulletin because I got tired of dealing with other software that was bug-filled and riddled with holes and security flaws. I spent hundreds of hours working on fixing problems in my spare time. I can also achieve my goals with vbulletin much faster 1/20th the time because this "just works." whereas before it was hit-and-miss 100% of the time.
On the moderator situatino, I've been part of many forums (under various usernames) that in a situation like what I referred to, one would contact a moderator, and the moderator would contact the offending party - act as an arbitrator in matters. Of course, I've seen some pretty childish things as well. :P