Do not feed the forum trolls

[Bill]

Facebook's description pretty well sums it up:
An "Internet troll" or "Forum Troll" is a person who posts outrageous message to bait people to answer. Trolls delight in sowing discord on the forums. A troll is someone who inspires flaming rhetoric, someone who is purposely provoking and pulling people into flaming discussion.
Signs Someone Is Trolling by howtogeekdotcom
It can sometimes become difficult to tell the difference between a troll and someone who just genuinely wants to argue about a topic. However, here are a few tell-tale signs that someone is actively trolling.

Off-topic remarks: Completely going off-topic from the subject at hand. This is done to annoy and disrupt other posters.
Refusal to acknowledge evidence: Even when presented with hard, cold facts, they ignore this and pretend like they never saw it.
Dismissive, condescending tone: An early indicator of a troll was that they would ask an angry responder, "Why you mad, bro?" This is a method done to provoke someone even more, as a way of dismissing their argument altogether.
Use of unrelated images or memes: They reply to others with memes, images, and gifs. This is especially true if done in response to a very long text post.
Seeming obliviousness: They seem oblivious that most people are in disagreement with them. Also, trolls rarely get mad or provoked.

The list above is by no means definitive. There are a lot of other ways to identify that someone is trolling. Generally, if someone seems disingenuous, uninterested in a real discussion, and provocative on purpose, they're likely an internet troll.