Despite emerging use of review replying function in online course eWOM, little attention has been paid to its role. The lack of theoretical researches and contradictory views have caused great inconsistencies in practice. The research designed two studies to explore the impact of review replying. Based on real data crawled, study 1 explored the relationship between review replying and learners' satisfaction. Based on social presence theory, study 2 analyzed the mediating effects of social presence and perceived learning between review replies and learning satisfaction, as well as the moderating effects of learners' participation degree. The two studies provide empirical evidence that review replying could increase learning perception and learning satisfaction by enhancing learners' social presence, no matter they are commenters (posters and repliers) or divers. Qualitative features (what people say) instead of numeric features (how much people say) of review replying determine how learners feel about online courses. The findings of research suggest online course providers to adopt review replying function as a new interactive tool, and encourage learners to engage in vivid and emotionally charged eWOM communication.