Useful practice: Systematize credibility assessments. Find ways to track the sincerity and accuracy of what people have said in the past, and make such information widely available. (An example from the legal domain would be a database of expert witnesses, which includes the number of times courts have qualified them as experts on a particular subject, and the number of times courts adopted or rejected their conclusions.) To the extent such info is widely available, it both helps to "sterilize" the information coming from untrustworthy sources and to promote the contributions that are most likely to be helpful. It also helps improve the incentive structure of truth-seeking discussions.