Oh, looks like you can get discussion on a post, and it's threaded, too, simply by virtue of replies being themselves posts that you can reply to.

TBH I did like unthreaded replies on G+; it was more like a normal conversation.

Also, I think that the editor expects single newlines, but doesn't visually display that quite like it'll end up in a published post. I have a habit, from text editors, of doing double-newlines! So I thought, based on the look of the editor, that I should, and then the resultant post looked spaaaaaaaced ouuuuuuuut.

Also, cmd-return doesn't post. Let's see if ctrl-return does. Nope!