If you troll on everyone else's posts without posting anything of your own, you could be sadistic.
“Trolling” is a term born of social media, and as such, it has become a hot topic in the world of psychology. Internet trolls go around writing negative comments on other people’s posts with the intent of inciting anger or simply to upset others. Most people view such individuals with disdain, and psychological analyses now back these beliefs: people who troll have major personality issues. These kinds of people actively enjoy hurting others and were found to have higher levels of narcissism, sadism, and psychopathy (according to a study done by a Canadian research team). Even people who aren’t so evil in their comments are likely to have some issue if all they do is comment without posting anything of their own. This behavior could be a sign of shyness and emotional sensitivity in a person, and they are thus often very attentive and strive to remember the information they encounter.