Is not necessarily a troll.
I've noticed in a lot of online interactions (that occasionally bleed off the screen into the flesh world) that people tend to use "troll" as a catch-all for a. people who are legitimately trolling you and b. people who are criticizing you / saying something you don't agree with.
The difference is, I would argue, intention. If the person sets out to annoy you or derail or whatever for their personal enjoyment, sometimes called the lulz, they are a troll. If a person is criticizing you and backing up their points by critically examining your language or character, they might be doing it in a jerky way, but that means they are actually putting forth effort into conversing with you. Ideally, it's because they hope you can be better.
A legitimate troll is trying to create an emotional response from you for their own benefit. A person who is criticizing you might be doing the same thing, but they're also doing it for your benefit. Or, at the very least if they think you're absolutely the fucking worst, the benefit of those reading, who will ideally be better.
ETA: It has been pointed out, appropriately, that there are people who sound like trolls but legitimately believe that kind of bullshit. Sometimes, they come in the form of someone you love (a family member, a friend, or heaven forbid that fleshbag you're fucking). That is.. well.. welcome to the world, we inhabit it with a lot of asshole.
So please, dear internetters, let's not use troll as a catch all when we really mean "this asshole right here". Just use the word asshole.
Vonnegut loved assholes. His is pictured here: