How Platform Affordances Shape Expression Effects: Comment Length and Audience in Political News Engagement

This experiment (N = 775) examined how commenting affordances shape expression effects in political news. Participants were assigned to conditions that varied comment length (short vs. long) and audience type (private, public, ingroup, or outgroup) on a simulated news platform. Composition and release affordances interacted rather than operating independently: short ingroup-directed comments were associated with less anger and greater enthusiasm, whereas longer private comments heightened affective polarization relative to public ones. A computational linguistic analysis revealed distinct word-use patterns across conditions. Findings establish the contingent structure of expression effects and advance a mass–interpersonal–intrapersonal framework, with implications for news platform design.