One system that appears to meet your needs is Joomla Community Builder with the Simple Machines Forum plugin.
This gives you a fully configurable forum including multiple ways of configuring Karma/Reputation, etc. It also gives you the community features that would potentially facilitate the rationalist meetups that you mention.
This gives you a fully configurable forum including multiple ways of configuring Karma/Reputation, etc. It also gives you the community features that would potentially facilitate the rationalist meetups that you mention.