Post-January 6 deplatforming shows long-term effects on ideological polarization among Twitter users.

This study examines audience response to Twitter's "Great Deplatforming" following the January 6 attack on the US Capitol. Using a survey of Twitter users from the 2020 US election, we test whether Twitter's deplatforming coincides with significant changes in respondents' behavior, operationalized using individuals' posting frequency and ideological lean-measured daily via a news-sharing metric we validate. To control for exogenous changes in the information environment, we pair Twitter respondents with Reddit accounts that exhibit similar pre-event behavior. Results indicate a shift in Twitter's ideological landscape: Respondents become more extreme, and polarization between liberals and conservatives intensifies as ideologically extreme users move further from the center. As the Great Deplatforming recedes, our Twitter users trend toward the center, suggesting that, while the platform experiences an immediate shock, it ultimately undergoes a long-term moderating effect. Importantly, these effects do not appear on Reddit, which instead exhibits an immediate reduction in ideological extremity following January 6th and sees no changes in longer-term trends. We also do not find evidence of a uniform flight from Twitter; only conservative-leaning respondents are significantly less likely to remain active. While results show ideologically extreme Twitter accounts experience some suppressive effect in activity, these effects seem specific to the most extreme actors, as decreasing trends among middle-of-the-road actors are present in both Twitter and Reddit. Taken together, while Twitter did experience a significant increase in the level of polarization and ideological extremity, the long-term trend appears to be one of moderation, an effect absent from Reddit.