Abstract: Online discussions are performed under the gaze of fellow users. To increase engagement, platforms often let users evaluate the comments made by others through rating systems, such as Likes or Down/Up votes. Understanding how such ratings shape, and are shaped by, features of the underlying discussion is important for our understanding of online behavior. In two studies, I focus on increasingly concerning aspects of online discussions: incivility and toxic language use. In the first study, I draw on the theory of normative social behavior (TNSB) to analyze over 6,000 online news comments. I find that repeated incivility by the same person is more likely when their initial incivility was affirmed by both descriptive norms (incivility in nearby comments) and injunctive norms (Up votes). In a second study, I apply this empirical framework to discussions on Twitter and Reddit surrounding the January 6th capitol riots. I find evidence that TNSB drives toxic commenting on Twitter, but less so on Reddit. Twitter users appear to be more reactive than Reddit users, which may be the reason why discussions on Twitter are more likely to feature sustained cascading of toxic comments. I discuss several mechanisms that could explain why social norms are more influential on Twitter than on Reddit.