I've noticed that discussion forums where everyone tries to be "nice"tend to degenerate into places where all criticism has to be phrased meekly and thus forthright criticism becomes impossible.

I won't deny that this particular attractor exists; that's why I think some degree of trollishness cannot be avoided. It would be enough if a fraction of members voluntarily adopt Crocker's Rules and serve as free targets for vigorous debate. These users would have to be largely uninterested in conventional status, since low status would be integral to their role.

However, we could take this idea to the extreme and award the lowest status to people with the best truth-seeking record and to the people who technically control the site; these people would be the "lowest troll(s)" and 'officially' heckle misguided and dishonest commenters who could not be discouraged by nicer means. The idea is that a ban (as a last resort) could afterwards be considered "fair", since it would be less affected by ostracizing, ingroups/outgroups and other spurious "community" dynamics.