This comment discusses the impact of social media rule enforcement protocols on research on online data sources. It argues that the conclusions of the article ‘Do Islamic State's Deadly Attacks Disengage, Deter, or Mobilize Supporters?’ concerning the recruitment effects of deadly attacks cannot be assumed to hold when considering the timing of Twitter account suspensions. It highlights four ways in which suspensions can confound evidence of demobilization despite the introduction of control variables and fixed-effects model specifications. All change the composition of the sample in four non-random ways. First, suspending connected Islamic State accounts may result in follower loss. Secondly, Twitter suspension procedures may be tied to account characteristics, such as follower accrual rates. Thirdly, suspended accounts that re-emerge introduce replication bias. Fourthly, account closure may reflect user movement to other platforms in response to changing security environments following deadly attacks. In conclusion, caution is advised when platform-introduced variation risks altering the sample composition in non-random ways.