If a night has a bringer rule, do you want that stated before you apply?
I think the useful version of a bringer night is boringly clear about it: how many people, whether they have to stay, and whether it applies to every spot. The annoying version is finding out after you’ve already arranged the evening. If you’re deciding whether to apply for an open mic, does a bringer requirement put you off automatically, or is it mainly the surprise/ambiguity that bothers you?