The Co-Intelligence Institute: Why is a fishbowl more productive than debate? The small group conversations in the fishbowl tend to de-personalize the issue and reduce the stress level, making people’s statements more cogent. Since people are talking with their fellow partisans, they get less caught up in wasteful adversarial games.
Participation in online forums tends to follow a “power law,” with vastly unequal engagement. If you want to counteract this tendency, one possibility would simply be for the most active participants to step back, and moderate how much they speak. This is related the the Carrying Capacity pattern and the Misunderstanding Power anti-pattern: check those out before you proceed. Occupy Wall Street used a related technique that they called the “progressive stack.” There are lots of other strategies to try.