"However, no one seems to know or be able to spell out exactly what this truly awful thing might be"

well...If I understand correctly, you do..or did...moderate/organize a music session somewhere?

Did you ever have an attendee who showed up regularly and did something that drove others AND the moderator batty? Playing when he shouldn't; playing out of tune; playing or singing the same piece every time he came, even if everyone had heard it 327 times? And when he was asked to alter this behavior, said "this is OUR session in a public venue, you have no business "imposing your judgment of what is proper on me." ?

Maybe not that PRECISE set of circumstances...but...*smile*...anyone who has ever run a music session has had to deal with something like that. They either make rules and announce them or they suffer...and if no one is allowed to deny the offender entrance, they suffer anyway.

Need I spell out the similarities in detail? "Truly awful" is subjective, but when 90%+ have the same basic opinion, it should tell you something. YOU know when a musician is behaving in a tedious manner, as we know when a fellow poster is doing likewise.

(As I have mentioned before, I have no delusions that this example, any more than others, will alter your perception of the issue ONE WHIT!) ,,,but you asked.