[Thunderbolt General] mounttimp:
The term "troll" can have a double meaning, related to fishing and ugly monsters. Both are appropriate.

"Troll," in the context of message boards and the like, describes somebody who is posting just to be confrontational or to raise hackles. One example might be a teenager who finds a Jewish message board and posts, "The Holocaust never happened." The teen may not know or care one way or the other--he just wants a reaction. He wants to piss people off. He is a troll.

There are more subtle trolling techniques as well. One Internet dictionary gives a real example in which somebody posted about "the discovery of an ancient African carving containing a list of prime numbers." The poster listed some of the prime numbers supposedly on the carving, some of which weren't actually primes. People who saw the message, thinking he was serious, responded with corrections. The troll then announced that those who spent their time responding to him had been "hooked."

That suggests how the term got its start. Trolling, to those who don't spend all their time in front of the computer, is a method of fishing where you trail bait through the water from a slow-moving boat hoping to hook an unwary fish. An online troll does much the same.

The other meaning of troll--a brutish monster who lives under a bridge--likely didn't have much to do with the origin of the term. But at an early stage it was conflated with the other sense of trolling for obvious reasons: if you've dealt much with trolls, you know you're dealing with some pretty ugly minds.

To be fair, not all trolls are slimeballs. On some message boards, veteran posters with a mischievous bent occasionally go "newbie trolling." On the Usenet newsgroup alt.folklore.urban, as of a few years ago anyway, it was fairly common for pranksters to post known urban legends as fact in hopes of getting novice users to go, "No, REALLY?" Gotcha, sucker.

The main point about trolls is that they intentionally mislead others. As the Free Online Dictionary of Computing notes, "Trolling aims to elicit an emotional reaction from those with a hair-trigger on the reply key. A really subtle troll makes some people lose their minds."

"Troll" is often flung about too casually. If somebody is simply ignorant or obtuse, it's incorrect to call him a troll. Admittedly, it's not always easy to distinguish between someone pretending to be wrong and someone who is wrong and doesn't know it or won't admit it.

How does one deal with trolls? That depends on your personality, the overall disposition of the message board, and the type of message board you're using.

There are two kinds of message boards: moderated and unmoderated. On unmoderated MBs such as most Usenet newsgroups, no one is in charge and there is no way to prevent a troll from posting short of persuading his Internet service provider to cancel his account. Moderated boards like the Straight Dope Message Board offer more control--truly egregious trolls can be banned and their posts deleted. But most board moderators, including those at the SDMB, reserve that sanction for extreme cases. A post I consider trolling someone else may find thought-provoking. Too quick a finger on the "delete" button and you open yourself to charges of censorship.

Besides, this is the Internet, the closest we've come to a free marketplace of ideas. The prevailing ethic here is that it's best to let everyone have his say, and rely on the good sense of other participants to sort out sound ideas from stupid ones. Which means it all comes down to you.

Many people feel trolls should simply be ignored, and some message boards have evolved their own private codes to warn off other users. (On the SDMB, one such code is DNFTT, "do not feed the trolls"). But others dislike the idea of giving trolls free rein.

On the SDMB, Cecil's goal of fighting ignorance is generally the guiding principle. If somebody posts misinformation, other users feel obliged to point it out. I'm sure some trolls delight in getting others to respond in this way, but the choice is either that or let a troll's posts stand unchallenged. Ignoring obvious nonsense has some advantages, but what about naive users who may read the falsehood and, seeing nothing to rebut it, believe it? To prevent that, some advocate responding to trolls once and only once. You refute the misinformation and that's that. Of course, this is often easier said than done, and many people (myself included) simply cannot sit idly by while the troll gleefully continues to post BS.

The other option is to pounce on every last falsehood and fabrication. This can lead to a classic flame war. We've had threads on the SDMB with close to a thousand posts as users attempt to get in the last word with an obstinate troll. These battles can be exhilarating but also exhausting. Inevitably at some point you ask yourself: what's the point?

In short, you've got two possibilities--ignore the troll or argue with him. My recommendation is as follows: If the person is a well-known troll with low credibility, post once to point out the flaws and then ignore him. If there's a real chance he may fool people who don't know better, knock him down with facts.