I've recently stumbled across the platform Change A View, which is a subreddit that forked/graduated to its own website that is centered around the idea of people creating posts in which they ask to have their mind changed. This tends to create a frame that enables much more healthy discourse than most online discussion.
Their new platform is centered around the ideas of "deltas" which users can award to other users when their minds have been changed by them.
I've surfed around the site a bit and generally found it pretty enjoyable and figured other people might find it valuable to. It's also an interesting for studying the psychology of what changes people's minds and what facilitates good discourse.