Contrarian Warning Sign Number Four, from the link above (dated 2006, but of course I’ve seen this since the days of Usenet):
The Contrarian Troll. A sophisticated breed, Contrarian Trolls frequent boards whose predominant opinions are contrary to their own. A forum dominated by those who support firearms and knife rights, for example, will invariably be visited by Contrarian Trolls espousing their beliefs in the benefits of gun control. It is important to distinguish between dissenters and actual Contrarian Trolls, however; the Contrarian is not categorized as a troll because of his or her dissenting opinions, but due to the manner in which he or she behaves:
– Contrarian Warning Sign Number One: The most important indicator of a poster’s Contrarian Troll status is his constant use of subtle and not-so-subtle insults, a technique intended to make people angry. Contrarians will resist the urge to be insulting at first, but as their post count increases, they become more and more abusive of those with whom they disagree. Most often they initiate the insults in the course of what has been a civil, if heated, debate to that point.
– Contrarian Warning Sign Number Two: Constant references to the forum membership as monolithic. “You guys are all just [descriptor].” “You’re a lynch mob.” “You all just want to ridicule anyone who disagrees with you.”
– Contrarian Warning Sign Number Three: Intellectual dishonesty. This is only a mild indicator that is not limited to trolls, but Contrarians display it to a high degree. They will lie about things they’ve said, pull posts out of context in a manner that changes their meanings significantly, and generally ignore any points for which they have no ready answers.
– Contrarian Warning Sign Number Four: Accusing the accusers. When confronted with their trolling, trolls immediately respond that it is the accusers who are trolls (see Natural Predators below). Often the Contrarian will single out his most vocal opponent and claim that while he can respect his other opponents, this one in particular is beneath his notice.
– Contrarian Warning Sign Number Five: Attempts to condescend. The Contrarian will seek refuge in condescending remarks that repeatedly scorn his or her critics as beneath notice – all the while continuing to respond to them.
– Contrarian Warning Sign Number Six: One distinctive mark of Contrarian Trolls is that every thread in which they dissent quickly devolves into a debate about who is trolling whom. In the course of such a debate the Contrarian will display many of the other Warning Signs mentioned above.