Platform ecosystems are characterized by knowledge boundaries that arise between the platform owner and third-party developers. Although major platform owners such as Microsoft and SAP nurture sponsored online communities to overcome knowledge boundaries in their ecosystem, the peculiarities of such communities are yet to be examined. Drawing upon the lead user and media richness theory, we investigate how different user roles and media types influence the value of a knowledge contribution in such communities. Analyzing one million answers from the SAP Community, we uncovered that both lead users and sponsor representatives are more likely to provide valuable knowledge contributions compared to normal users. Moreover, we show that attachments, code snippets, and links significantly enhance the value of a knowledge contribution. Surprisingly, we find a strong negative moderation effect of code snippets on the contributions of sponsor representatives, but a strong positive moderation effect on the contributions of lead users.