I think they sometimes help raising awareness about the fact that trolls can only exist if people feed them. "Don't feed the troll" is such a correct statement. But it does look offensive to the alleged troll, so there's a thin line here, which is difficult to be objective about.
troll detectors

At the risk of igniting those very arguments about trolling, perhaps you could post a discreet "Don't feed the "Don't feed the troll" anti-troll" graphic.
do we really need those self pro claimed troll detector on chess.com forum.
I have seen some topics where the "troll detector" misunderstood the topic and suddenly posted troll information totally off topic and ruining the topic because you have to scroll a large ugly picture.
furthermore it has the downside that it bumps the thread because it is a new post and you may not notice another post.
sometime the troll detector and the accused troll spent time on arguing again very off topic to the topic being discussed.
I don't think that posting info on trolls will stop people that are indeed trolls. but I guess we have forum administrators who can say something.
I think everything in here is a friendly envorenment and people can think for themself.