For now I’ve closed the “general” channel — that’s the chat channel that automatically added all users. I have found chat DMs to be useful in the past.
If there’s a consensus to choose to start using chat I’ll be happy to re-enable the whole-board chat, but this was just a new feature of Discourse that was auto-enabled during some auto-upgrade a while back.
It’s also worth noting there’s a good deal of site-wide customizability that we can do here (but we haven’t intentionally done anything).