Emotion, visibility, and epistemic salience on X and Bluesky. Knowledge circulation around the Italian citizenship referendum

In this post-digital era, algorithms have emerged as decisive epistemic agents in shaping public knowledge and reconfiguring the conditions under which social discourse is produced, validated, and made publicly credible. This study investigates digital platforms as epistemic infrastructures, exploring how algorithmic mediation reshapes visibility and authority. Through a comparative analysis of X and Bluesky during the 2025 Italian citizenship referendum, we operationalize epistemic salience using Gini coefficients and emotional affect analysis on a dataset of 2224 posts. Findings reveal that while both platforms exhibit high engagement concentration, X functions as a stable, rigid oligarchy, whereas Bluesky maintains a more fluid and decentralized ecosystem. Notably, the referendum triggered a temporary democratizing effect on both platforms, increasing pluralism during the peak of the campaign. Furthermore, while negative emotions – particularly Anger – characterize the dominant discourse on X (84%) and are more likely among anti-reform supporters, regression models indicate that structural factors (follower base and platform logic) remain the primary drivers of engagement over affective content. These results demonstrate that platform architecture acts as non-neutral epistemic filters: while Bluesky fosters a more pluralistic and positive environment, X’s infrastructure reinforces a persistent elite-driven and affective narrative. Ultimately, the epistemic salience in nowadays democratic discourse is co-shaped by infrastructural algorithmic gatekeeping and human emotionally driven democratic deliberation.