  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.
