Organizational identity is always somewhat socially co-authored. The social-media context provides an opportunity to interrogate the extent of this co-authoring in an interaction-heavy and difficult to control environment. This article presents a typology of online communities that co-author organizational identity through confirming and disconfirming identity messages. Through extensive qualitative research, including interviews, marketing meetings observations, and social media interaction observations, social media communicative practices are examined through a communication constitutive of organizing (CCO) framework, specifically the conversation-text dialectic of the Montreal School. By focusing the research on boundary-spanning social media marketers and their interpretations of social media interactions, this article demonstrates ways that organizational identities are co-authored from external interaction (conversation) to internal practice (text). This study contributes to the ongoing theoretical extension of the CCO framework beyond the container metaphor, while also contributing to the practice of social media marketing within and around organizations.