Do you have one and do you follow it?
I ask because I have sort of considerations, however what I expect from others isn't what I do, let me try and explain.
I normal meet 1 person in game and through them I play with others they play with, so i end up playing with various groups of people.
When I am in a party I don't have a problem with anyone joining the party to chat or play, infact I welcome it and most know if the chat needs to focus due to the game the idle chit chat gets asked to stop and everyone I play with seems fine with that and either stays and waits for a time or leaves and waits for a better time.
However I always feel like its better to be invited than just bounce in, more so when i haven't played with someone for a while.
I do send messages asking if people mind me joining just incase.
Do you have a party chat etiquette, and what do you expect?