Debates involve trying to make a case to prove your point. Discussions involve many people offering opinions, not generally intended to get anyone else to side with them.

The need to refute is something I consider a characteristic of a debate. The incessant back-and-forth. Offer an opinion, maybe comment on somebody else's, then leave it, if you intend to discuss.

I think some people don't have that much to say, unless they can go after another person's opinion. Sometimes they seem to show up in a thread simply because their constant opponent is involved. I don't think it's possible to have a "discussion" here these days. Too many people who want to compete.