I like the Discourse approach. http://www.discourse.org/ http://www.discourse.org/ Instead of nested replies, it encourages "Creating new threads linking back

I like the Discourse approach. http://www.discourse.org/ http://www.discourse.org/ Instead of nested replies, it encourages "Creating new threads linking back to a post", which I find to be way more orderly than "conversation trees". They're also aiming for feature-parity with mailing lists, allowing people to participate effectively with threads by e-mail alone.