ABSTRACT Drawing upon the social identity model of deindividuation effects, this study investigated the effects of intergroup relations and discursive quality on individuals’ responses to comments that challenge their existing beliefs on news websites. A two-session online experiment with a 2 (group membership: in-group vs. out-group) × 2 (comment tone: civil vs. uncivil) between-subjects factorial design was conducted. The results showed that exposure to counter-attitudinal comments from in-group members, compared to out-group members, led to greater opinion conformity and less expression of disagreement. Additionally, there was a significant interaction between group membership and comment tone on disagreement expression. When counter-attitudinal comments were uncivil, individuals exposed to in-group comments expressed less dissent in their replies than those exposed to out-group comments. This tendency, however, was not significant when the counter-attitudinal comments were expressed in a civil tone.