Large-scale online platforms powered by user-generated content are extensively researched as venues of learning and knowledge production. In this ethnographically oriented study, we examine knowledge practices on a community question answering platform for computer programmers in relation to the platform mechanics of voting. Grounded in the practice theoretical perspective and drawing on the analysis of online discussion threads and platform-related online materials, our study unpacks the dominant practice of crowd-based curation, the complementing practice of distributed moderation, and the more marginal practice of providing feedback to content producers. The practices co-exist in tension and consonance, which are embedded in the materiality of the platform and are continuously enacted through user discursive boundary work, sustaining the mentioned practices as intelligible for other users, and outlining what counts as legitimately participation on the platform. The study contributes to existing research on the roles voting plays on online platforms, as well as offers implications for research on social and material organization of users' online practices. The study also discusses that it is the ambiguity around the mechanics of voting that allows practices to co-exist. While this ambiguity is often discussed by users as problematic, we suggest as potential implication of our study that it may be productive to design platforms for workable forms of ambiguity allowing knowledge practices to co-exist in tension and to provide space for user negotiations of these practices.