A "troll" is not a person, it is a post. Fishing ships with big nets are called "trawlers," and they "troll" for fish by sailing through the ocean grabbing everything that lands in their net. A "troll" post is a post designed to get responses from readers rather than provide any useful information or further the discussion in some way. No, we have no use for trolls. Say something interesting, don't just try to get our attention by acting like a geek.
They're certainly as dumb as a fence post.