Norm Violations in Online Discourse: Epistemic and Civil Foundations for Platform Design and Moderation

Fostering healthy online conversations is essential to the integrity of public discourse, yet the norms that guide such conversations remain contested and difficult to enforce. This paper develops and empirically grounds a conceptual and empirical framework for understanding and addressing online toxicity. Building on the distinction between epistemic and civil norms, we argue that norm violations are the proper target of moderation. While this paper is primarily conceptual, it is informed by empirical observations drawn from a collaboration with a platform designer. Drawing on a dataset of user comments and responses to moderation scenarios, we identify eight recurring types of norm violations and analyse patterns of user agreements about whether such content should be removed. Our findings reveal that while civil norm violations prompt relatively consistent responses, epistemic violations elicit wide disagreement, raising challenges for universal moderation standards. We conclude by proposing a set of general, evidence-informed principles for platform designers and moderators. These recommendations emphasise context-sensitive moderation, platform affordances that encourage epistemic responsibility, and the integration of civil and epistemic considerations into online infrastructure. Our work bridges theoretical and practical perspectives, offering both conceptual clarity and actionable insights for scholars, designers, and practitioners engaged in shaping healthier digital discourse.