Whatever the group chat tolerates becomes the group chat’s culture. Somebody decides that. Might as well be you.

Group norms are not written anywhere. They get set by what happens the first few times somebody crosses a line: if nothing happens, the line moved, and now that is what the chat is. Everyone assumes somebody else will say something and nobody does, so the drift keeps going. There is no committee, only whoever speaks first.

When something lands badly this week, be the one who says so, plainly and without a lecture. A short line is enough. You will feel like the serious one for about a minute, and then other people usually agree, because most of them were uncomfortable too.