Online social media foster the creation of active communities around shared narratives. Such communities may turn into incubators for conspiracy theories -- some spreading violent messages that could sharpen the debate and potentially harm society. To face these phenomena, most social media platforms implemented moderation policies, ranging from posting warning labels up to deplatforming, i.e., permanently banning users. Assessing the effectiveness of content moderation is crucial for balancing societal safety while preserving the right to free speech. In this paper, we compare the shift in behavior of users affected by the ban of two large communities on Reddit, GreatAwakening and FatPeopleHate, which were dedicated to spreading the QAnon conspiracy and body-shaming individuals, respectively. Following the ban, both communities partially migrated to Voat, an unmoderated Reddit clone. We estimate how many users migrate, finding that users in the conspiracy community are much more likely to leave Reddit altogether and join Voat. Then, we quantify the behavioral shift within Reddit and across Reddit and Voat by matching common users. Few migrating zealots drive the growth of the new GreatAwakening community on Voat, while this effect is absent for FatPeopleHate. Finally, conspiracy users migrating from Reddit tend to recreate their previous social network on Voat. Our findings suggest that banning conspiracy communities hosting violent content should be carefully designed, as these communities may be more resilient to deplatforming.

翻译：在线社交媒体促进了围绕共享叙事形成活跃社区。此类社区可能成为阴谋论的温床——其中一些传播暴力信息，可能加剧争论并潜在地危害社会。为应对这些现象，大多数社交媒体平台实施了内容审核策略，从发布警告标签到去平台化（即永久封禁用户）。评估内容审核的有效性，对于在平衡社会安全的同时保护言论自由至关重要。本文比较了Reddit上两个大型社区GreatAwakening和FatPeopleHate被封禁后用户行为的变化，这两个社区分别致力于传播QAnon阴谋论和进行人身羞辱。封禁后，这两个社区部分迁移至Voat——一个未加审核的Reddit克隆平台。我们估算了迁移用户数量，发现阴谋社区用户更可能完全离开Reddit并加入Voat。随后，通过匹配共同用户，我们量化了Reddit内部以及Reddit与Voat之间的行为转变。少数迁移的狂热分子推动了Voat上新的GreatAwakening社区的增长，而这一效应在FatPeopleHate中并不存在。最后，从Reddit迁移的阴谋用户倾向于在Voat上重建其先前的社交网络。我们的发现表明，封禁包含暴力内容的阴谋社区应谨慎设计，因为这些社区可能对去平台化更具韧性。