The non-music or 'BS' section was basically formed so that the lighter, more amusing threads could be housed in a safe and secure environment where they wouldn't leak contaminants (or "humour") in to the more serious music threads.

Not exactly.

The BS prefix was invented because a few posters complained about what others posted.

The split into two sections was invented because a few posters complained about what others posted.

I suspect that very the same posters are still compaining about what other posters choose to post. Only now such complaints are encouraged.