A mistake I've seen is when they try to suppress criticism as oppose to harness it. A classic thing I saw moderating in the original Valve forums was the first

A mistake I've seen is when they try to suppress criticism as oppose to harness it. A classic thing I saw moderating in the original Valve forums was the first time poster going on the all caps rant. 9 times out of 10 you could just talk to them calmly and turn them into an ally and make them know someone was actually listening. All they wanted was to be heard.