To identify a Troll. It is quite easy. They usually seek attention even if it is the negative kind of attention.
They even go as far as trying to get any type of reaction out of you. There are people immune to trolls/attention seekers. Those people usually don't give the reaction trolls expect and instead treat them like they would treat anyone else out there. (This is basically telling said troll they aren't special to them in any kind of way.)
When a troll doesn't annoy their victim/get the attention they were looking for then they get annoyed. Usually trolls have a low self esteem so they try to bring others to feel a bit how they do. But that is just false hopes as trolling will not change who they are in real life.
Plus making thousands of enemies thinking you are safe just for being anonymous is never a good idea when we live in a society that relies on helping each other. I also don't recommend trolling on the internet unless you have some knowledge about cyber security. Troll 1 wrong person and you can get hacked and your real life info plus image gets doxxed.
There is a saying, "when people wear a mask they become their real self" meaning that anonymity gives you false assurance that there will be no consequences. There are always consequences for everything even if you think you are being anonymous. But that is another topic.