This study investigates the organization of interaction through comments on the social networking site Facebook. Facebook offers a range of affordances that allow communication between users. These include written language in various settings (messaging, commenting, posting), as well as a range of non-verbal resources, such as uploading photos, sharing links, the "like"-button. Our analysis focuses on the post+commenting section, which users treat as a quasi-conversational space. Much as conversation is organized through the sequential unfolding of turns through time, the interaction in the comments section is organized according to a pattern that lets users "make sense" of the communication as a coherent exchange. This comment organizing mechanism, which is enacted through tying practices, operates on written language rather than spoken, and so needs to accommodate different affordances than turn-taking does: it has to be able to co-ordinate contributions not just through time, but through space as well. The theoretical significance of this research then is its exploration of a complex mechanism that is used by humans to maintain social order through writing and reading practices. In particular, it takes into account how the context of the website shapes people's communication through the resources made available. © 2015 Walter de Gruyter GmbH, Berlin/Boston.