I am presented with another person's responses to my inputs in the form of communications, and I build a model of the person. Sometimes this model is correct, sometimes this model is incorrect. I might misjudge a person who is kind to my face as being decent, when behind my back they spread rumors and gossip. Similarly, I might have a coworker who always criticizes my approaches to problems, but is the first to stick up for me in meetings.
Sometimes you judge rightly, other times wrongly, and in either event life goes on (real or virtual). This is just part of the human condition--and trolls remind us of this fact and the fact that sometimes you can't tell.
I'd imagine that those two are not a mutually exclusive set.
Besides, if a troll makes a reasonable point, does it matter that he was actually trolling? Truthfully it's snark that bothers me most - I can deal with someone being playful or contrary for the sake of it, but too much snark just triggers a very primal part of my brain that makes we want to start cracking skulls, and that's not very conducive to continuing the discussion.
