Network Structure, Addressivity, and Civility in Networked Publics

On open social media platforms, the convergence of diverse, often incompatible audiences—colleagues, family, strangers—within a single communicative space creates persistent challenges for civil expression. This longitudinal study examines how the structural properties of users' social networks and their use of addressivity (@mentions and replies) shaped communication civility on Twitter during the early 2010s. Drawing on a dataset of 1,827 user timelines with over 1,700 tweets each spanning approximately 4.4 years, we operationalize civility across four measures—offensive language, sensitive content, negative sentiment, and positive sentiment—and track how each individual's behavior changes over time. Our main finding challenges network closure theory: contrary to predictions derived from Coleman's closure argument that densely interconnected networks promote civility through heightened accountability, increased network constraint predicts less civil expression, suggesting that tightly knit networks foster in-group communicative norms that diverge from mainstream standards. By contrast, addressivity consistently promotes civil expression across all measures, supporting audience design and politeness theories and demonstrating their robustness in context-collapsed digital environments. Together, these findings demonstrate that civility on social media is a dynamic response to communicative context rather than a stable individual trait. The tight-knit network structures that promote accountability in face-to-face communication can have the opposite effect online, where group belonging encourages rather than discourages norm-deviant expression.