Detecting a chat room troll

Anyone who has ever posted in a chatroom knows about trolls. Trolls are mentally ill people who have fled into cyberspace to inflict their psychosis on the rest of us. The sole point of a discussion board is to serve as an electronic bar where ideas and information can be exchanged. The fact that people disagree makes for great boards. My major problem with Free Republic is that we end up agreeing too much.
Trolls are not about dissent they are about disruption and harassment. They come with multiple names and writing styles and harass the same posters. They talk to each other and pretend to form a fan club for each other. The rest of us have to deal with cluttered boards and annoying minutia.
Writting styles are like fingerprints and this is the achiles hell of a troll. The writting style can not vary as we have one brain and subtle clues in spelling and grammar are often evident. Repeated phrases that get repeated under various identities. A new name pops up and continues old grudges with familiar material. A noob wants to debate minutia like the political line vs circle theory. The point is to waste time rather than discuss substance.