Bonnie, you're gonna find that in an open session bad etiquette usually "wins". People playing too loud are going to drown out people playing at a lower level. One person playing out of tune or out of time, will often drag down a host of solid musicians. One player who refuses to sit out and take turns will keep playing, forcing others to either sit out or answer bad etiquette with more bad etiquette. (This last scenario comes up often with multiple bodhran players at a session.) ON a brighter note, people who show good etiquette at open sessions are more likely to be invited at closed sessions, house parties, dances etc.
If you keep your side of the street clean and play with others as opposed to playing over others or against others, in the long run you'll be better off and even in the immediate future, at least you're not part of the problem.
Cheers,
Rich