This study investigates a postulated 30% supportive-comment threshold as a “tipping point” for minority expression on social networking sites (SNSs) in the context of online incivility. By doing so, perceived hostility is introduced as an interactional factor explaining minority’s expression (un)likelihood. Results from a 2 (comment civility: civil vs uncivil) × 3 (supportive-comment proportion: 15% vs 30% vs 45%) (N = 807) revealed that perceived hostility from uncivil comments is lowered at the 30% supportive threshold, which then leads to greater likelihood of public expression by minority opinion holders (i.e. moderated mediation). Supportive-comment proportions were, however, not found to directly affect perceived hostility in civilized discussions. Overall, minority opinion holders are more likely to react via emojis (Like, Love, Haha, Wow, Sad, Angry) in SNSs than to post comments. The implications of findings for the spiral of silence in online settings are discussed.