<p>This study examines the relationship between online social interactions, sentiment dissemination, and stock market returns using Reddit data. We find that a small number of active users significantly influence others by disseminating sentiment within their networks. Active users have a more pronounced influence on less-active users when they share similar beliefs and during periods of increased uncertainty. Moreover, we show that prior-day abnormal network sentiment positively affects future stock market returns. Finally, we evaluate a network-based market timing strategy that effectively reduces drawdowns and highlights the practical implications of online interactions.</p>