The entangled dynamics leading to the sedimentation of polarisation on political Reddit

Motivated by the dearth of research providing a comprehensive assessment of how various aspects of Reddit contribute to political polarisation on the platform, this study examines the dynamics of cross-ideological communication across 11 major subreddits over 16 years. Going beyond purely textual elements, we analyse a broad range of possibilities for overlaps between subreddits. This includes common users, information-sharing, cross-posting, cross-commenting, links to other subreddits, and discursive identities. We observe minimal overlaps in all these indicators. This is true even for subreddits with highly similar discourses and extends beyond a left-right dichotomy. These patterns, we argue, emerge from an entanglement of platform design, moderation practices, user agency, discourses, and broader socio-political contexts. Our findings show how this entanglement leads to the sedimentation of polarisation on Reddit, wherein the fragmentation of political subreddits is irreducible to discourses, identities, or platform design alone. These findings also challenge the common framing of r/politics as a town square for cross-ideological deliberation and exposure.