When laypersons are interested in science-related questions, they frequently visit participatory websites such as science blogs. Typically, articles on these sites are accompanied by user comments or ratings. The present research investigated the effects of different forms of user feedback on readers’ interpretation of science topics. In two experiments (N = 178), participants read a one-sided blog article about the dangers of violent video games. The visible user reactions contradicted the slant of the article and were systematically varied (argumentative comments vs. subjective comments vs. ratings vs. none). Results of Study 1 showed that parents (for whom the topic is relevant) made use of comments and ratings to infer the opinion climate, while there were only limited effects on readers’ attitudes. Less involved readers (student participants in Study 2), in contrast, were susceptible to the persuasive influence of user comments. Implications regarding the role of user reactions in online science communication are discussed.