Utilizing data from the East Money stock forum, one of China's most influential financial portals, this study examines how online discussions among individual investors influence managerial learning from stock prices to make investment decisions. We find that higher discussion intensity is associated with lower investment-q sensitivity, indicating that investors' online discussions impede managerial learning from prices. This effect operates through a decline in information asymmetry and the probability of informed trading. Furthermore, the negative impact is more pronounced when managers exhibit stronger incentives to learn from market signals. Overall, our findings support a crowding-out mechanism: online discussions crowd out the private information gathering of informed traders, thereby reducing the informativeness of prices for real investment decisions.

We examine a unique phenomenon among exchange traded funds (ETFs) in the Chinese stock market, finding that ETFs pervasively participate in initial public offerings (IPOs) to profit from underpricing. The ETF IPO participation passes primary market benefits to retail investors, providing benefits from hard-to-reach investment opportunities. These active moves showing ETFs are not entirely passive highlight the gains of the active management. However, we observe that this activity leads to increased non-fundamental volatility and short-term return reversals, as well as decreased investment-q sensitivity among ETF member stocks, presenting a negative externality. Using a policy shock as the quasi-natural experiment, we establish the causality of these effects, underscoring the dual nature of ETFs active management.