Echo chamber formation sharpened by priority users.

On social media platforms, priority users (e.g., verified profiles on X) are users whose posts are promoted by recommendation algorithms. However, their influence on opinion dynamics, in particular polarization and echo chamber formation, is not well understood. Through computational modeling, we investigate this influence in a stylized setting. By introducing priority user accounts, we find that prioritization can mitigate polarization. However, by incorporating stubborn user behavior, we find that the results change and that priority accounts can exacerbate the formation of echo chambers. In other words, a minority of extremist ideologues can trigger a transition from consensus to polarization. Our study suggests careful monitoring of platform prioritization policies to prevent potential misuse of users with enhanced influence.