Where things go.
Discord is the kitchen — fast, social, real-time. Use it for: hellos, scheduling, immediate questions, vibes, photos, “anyone around for a call?”, quick links, working-group standup chatter.
Discourse (this site) is the workshop — slow, persistent, citable. Use it for: drafts and proposals, decisions, working-group agendas and notes, long arguments worth keeping, source documents, mutual aid requests that need to stay open more than a day, and anything you want findable in six months.
Rule of thumb: if you’d want to quote it in a meeting, put it in Discourse. If you’d be embarrassed if it were quoted in a meeting, you probably shouldn’t post it in either.