> What do they gain from causing such discomfort to others?
Most people play some kinds of irrational games to generate emotions they are addicted to. The difference is what kind of emotions they want, and what kind of scenarios they use to obtain it. There is a popular book on this topic called "Games People Play", strongly recommended.
From the psychoanalytical perspective, all these games ultimately are sick attempts to indirectly extract symbols of love, when people are too afraid of a more direct approach (aren't we all sometimes?).
The recipe for this specific game is that I cause you discomfort, and if you continue interacting with me anyway, it means that you have forgiven me (for causing you the discomfort), which means that you care about me (otherwise why would you keep interacting with me). So I frustrate you in order to extract a costly signal of caring from you, so that I can feel loved for a moment.
Why not a more direct approach? First, I am afraid to ask whether you care about me, because you might say no. Even worse, if you said yes, I would still be suspect that you are lying; maybe you are just being polite. But when I cleverly extract forgiveness from you, if you stay with me regardless of the discomfort I cause, then I can be sure that you genuinely care.
Of course, the damage caused to both sides by this approach is obvious. But sometimes people just don't know how to do it better, and any symbol of love is better than nothing.
If you will enjoy the book, I would recommend reading also the sequel "What Do You Say After You Say Hello?". It is much less famous, probably because it was published posthumously, but I liked it even more. It needs to be read later, though, because it heavily references the "Games People Play".
trolling can be a lot of fun. especially ideological adversaries. people will get incredibly twisted around their own axles And literally enraged over the opinion of some anonymous joker who they will never meet or have another interaction with. these feelings can follow you around for days vexing you and bringing you back to that negative state of mind. and that is hilarious to people who have learned to not give a shit about what some stranger thinks of them on the internet.
You have a lot of control over your own mind and emotions, so don't relinquish it to malevolent tricksters. And if you can't do that quit social media. but really everyone should quit social media probably.
Your discomfort is the point for them.
Quickly figuring out that you're in such an interaction and bailing before your day is ruined is the best you can hope for in the short term.