According to Wikipedia, "An Internet troll, or simply troll in Internet slang, is someone who intentionally posts controversial or contrary messages in an on-line community such as an on-line discussion forum with the intention of baiting users into an argumentative response."
There are problems with this concept. First, it is based on intent (why do you care about someone's intent?!). Second, it discourages discussion on controversial topics. Third, it seems to imply that debate is bad if it upsets some people.
So essentially, by accusing people of being trolls and discouraging them from further posts, you get discussion groups where posters have similar views and where debate is restricted to mostly minor issues.
That doesn't sound good at all.
Here's an example that shows up now and then:
Orig Post: "I'm trying to decide if I should locate my startup in silicon vally or in san francisco. I'd like to be near my potential buyers, which would mean locating in the valley. But I think my developers would be happier living in the city."
Here are two strong responses, one legit, and one from a troll:
Non-Troll: "San Francisco isn't as much fun as people make it out to be. I don't think it would help you attract developers at all. I'd much rather be in the valley where the action is."
Troll: "The city? San Francisco isn't a city. New York, now that's a city..."
Both of these posts are clearly going to attract some argumentative responses. The first may goad a few people, but it is on-topic, contains something that can be defended or refuted under the terms of the original debate, and continues the discussion. The second tries to provoke the thread into something kind of stupid and off-topic.
Argumentative people can further debate, but Trolls always degrade a discussion until there is no longer anything substantive.
I hope for the best for this discussion forum. Craigslist is essentially unusable because of the trolling, but hackernews is still pretty great.
Will hackernews be like that chilly bar you found that got overrun by jackasses six months later, forcing you to look for a new spot? Man, I hope not, because this is a good site.