Reward‐based crowdfunding provides a rich arena for co‐creation, where different types of dialogues between backers and project initiators aid crowdfunding performance. Nevertheless, research on how backers' co‐creation, in the form of comments, influences crowdfunding performance is still scarce. Based on signaling theory, this research investigates the impact of backers' specific co‐creation comments (we coded comments for co‐ideation, co‐evaluation, and co‐design) on crowdfunding performance. The present study also examines whether the timing of posting co‐creation comments influences associated performance benefits. We used a panel dataset of 446 reward‐based crowdfunding projects with 7254 observation days. The results show that backers' co‐ideation and co‐evaluation activity leads to a higher funding amount. Furthermore, the impact of co‐ideation is higher for comments made early in the project's lifecycle, while the effect of co‐design is wholly contingent on the time of commenting, with early co‐design comments contributing negatively to crowdfunding performance.