This feels like a common courtesy I don’t see enough, particularly the second point. In a conversation circle, always try to keep your side vision open to people trying to find their way in. It can be awkward to try and find your own way in so giving them a spot tells them they’re included then drop a quick brief on the conversation “We’re talking about pineapples on pizza, good or bad” gives them context to jump in immediately.
If there isn’t that special, outgoing and kind of goofy person in a group to do what you are saying, groups of fairly good intentioned people can just feel incredibly mean and unwelcoming. It is really weird when you are the new person and can see the group desperately needs people to be aware of these things but no one cares or is aware of it. Every one of the people in the group can be a friendly person but the group is effectively a mean clique.