Since I have for the last 40 years been a member of a very large & diverse folk society, I have always realized that at any gathering there was likely to be several singers who knew 'almost' any songs that I did, and probably did them better.
   Thus, I just sang what I could.. as best I could... and gradually figured out what to avoid in certain situations. Eventually, *I* came up with several that no one else in the group seemed to do, and discovered that some of those were 'learned' by others, but not done when I was present.
   So... I do see why the practice of deference to certain folks about certain songs grew up. I never treated it as a 'must be obeyed' law, but I can't help being aware of the way it works.