Online question-and-answer (Q&A) communities provide convenient and innovative ways for participants to share information and collaboratively solve problems with others. A growing challenge for those Q&A communities is to encourage and maintain ongoing user participation. From the perspective of motivational affordances, this study proposes a research framework to explain the effect of content commenting on user continuance behavior in online Q&A communities. The moderating role of participant's tenure in the relationship between content commenting and user continuance is also explored. Using a longitudinal panel dataset collected from a large online Q&A community, this research empirically tests the effect of content commenting on continued user participation in the Q&A community. The results show that both comment receipt and comment provisioning are important motivating factors for user continuance in the community. Specifically, received comments on questions submitted by a participant have a positive effect on the participant's continuance of posting questions, while answer comments both received and posted by a participant have positive impact on user continuance of posting answers in the community. In addition, tenure in the community is indeed found to have a significant negative moderating effect on the relationship between content commenting and user continuance. This research not only offers a more nuanced theoretical understanding of how content commenting affects continued user involvement and how participants' tenure in the community moderates the impact of content commenting, but also provides implications for improving user continuance in online Q&A communities.