@Centurion: I didn't say anyone could sue (in fact, I said the opposite), and I agree with your point. To clarify mine: this kind of action would merit lawsuits when taken out of the internet/gaming context and placed in the real world.
Ah, OK. I agree with you that defamation can definitely cause significant amounts of hurt in the real world. I can even imagine situations where punitive damages would seem justified though I don't know if they ever get rewarded for it.
@Hack: Publishing such accusations is libel - I'd say a public forum, which can be accessed by anyone, counts for that.
Note that if what you say is true, it is NOT libel. What you say has to be false or at least very misleading in some sort of way. So, if what How is saying about these people is true then it is not libel. "The truth will set you free." Of course, proving truth and non-truth in court is a very different matter.
Also, what about people who are new to the game and don't know him? Are they supposed to take these denunciations at face value without having ever met the villains in question?
Personally, I'd want to go find out for myself.