Oh, I think the in-group/out-group thing is huge. We are wired to be tribal, after all. I think we need platforms that help us overcome this by inviting the identification of common ground. Until those exist, social agreements about how to interact are our best hope, but those require a sense of community that many public domains do not support well.
As for Parlio, I was given two invites, which I’ve used up. But I will ask for more.