Current screenshot of r/fatpeoplehate, a subreddit that was banned by Reddit in 2015.

This blog post summarizes my full paper accepted at CSCW 2017, available here.

In 2015, Reddit closed several subreddits due to violations of Reddit’s anti-harassment policy. Foremost among them were r/fatpeoplehate and r/CoonTown: r/fatpeoplehate was a fat-shaming subreddit devoted to posting pictures of overweight people for ridicule, and r/CoonTown was a racist subreddit dedicated to violent hate speech against African Americans. However, the effectiveness of banning as a moderation approach remains unclear: banning might diminish hateful behavior, or it may relocate such behavior to different parts of the site. We studied the ban of r/fatpeoplehate and r/CoonTown in terms of its effect on both participating users and affected subreddits. Working from over 100M Reddit posts and comments, we generated hate speech lexicons to examine variations in hate speech usage via causal inference methods.

User-level Effects of the Ban

Following Reddit’s 2015 ban, a large, significant percentage of treatment users from banned communities left Reddit (as compared to a cohort of control users). For the banned community users that remained active, the ban drastically reduced the amount of hate speech they used across Reddit by a large and significant amount. Following the ban, Reddit saw a decrease of over 80% in the usage of hate words by r/fatpeoplehate and r/CoonTown users (relative to their control groups). The observed changes in hate speech usage were verified to be caused by the ban and not random chance, via permutation tests (see Appendix A in the paper for more details).

Community-level Effects of the Ban

Following the banning of r/fatpeoplehate and r/CoonTown, the affected users migrated to other parts of Reddit. The majority of r/CoonTown users migrated to other subreddits (like r/The_Donald, r/homeland, r/BlackCrimeMatters) where racist behavior has either been noted or is prevalent. On the other hand, most of the r/fatpeoplehate users migrated to qualitatively different subreddits dedicated to roasting users who voluntarily post pictures of themselves or others (r/RoastMe), gaming (r/fo4) or TV shows (r/MrRobot).

We observed no change in hate speech usage of migrants in the invaded subreddits post-ban, nor did we see any significant change in hate speech usage of preexisting users in these subreddits. In simpler terms, the migrants did not bring hate speech with them to their new communities, nor did the longtime residents pick it up from them. Reddit did not “spread the infection”.

Banning Subreddits ``Worked” for Reddit

For the definition of “work” framed by our research questions, the ban worked for Reddit. It succeeded at both a user-level and a community-level. Through the banning of subreddits which engaged in racism and fat-shaming, Reddit was able to reduce the prevalence of such behavior on the site. The amount of hate speech generated across Reddit by r/fatpeoplehate and r/CoonTown users went down drastically following the ban. By shutting down these echo chambers of hate, Reddit caused the people participating to either leave the site or dramatically change their linguistic behavior (as measured via our hate lexicons).

At a community-level, the ban also worked. The subreddits that inherited the activity of former r/fatpeoplehate and r/CoonTown users did not inherit their previous behavior. We examined users’ hate speech usage post-ban in new subreddits — hate speech previously largely confined to these two banned subreddits. When controlling for general trends in hate speech usage across Reddit, we found that the ban had no effect on the hate speech usage in subreddits invaded by migrants from r/fatpeoplehate.

Implications for Online Moderation

Reddit’s decision to ban r/fatpeoplehate and r/CoonTown — and thereby disperse participants to other parts of the site — reduced overall hate speech usage on the site. An implication for sites is that banning spaces where deviant groups congregate is likely to work. However, whether to ban groups for engaging in a behavior that the site considers deviant is a difficult and open question. To start with, who gets to define “deviant?” In our work, we have focused on the pragmatic effects of Reddit’s decision to ban r/fatpeoplehate and r/CoonTown, rather than if Reddit should have done it in the first place.

Ideas around freedom of speech online — and conversely, a platform’s responsibility to protect its users, community and brand from harm — are undergoing rapid negotiation. Some argue for nearly unrestricted freedom of speech on the internet, even surpassing what the most permissive liberal democracies allow. And yet, the platforms are usually owned by companies that have a financial stake in the ongoing success of the platform, as well as no obligation to uphold freedom of speech guarantees. The argument is complex and multifaceted, with many social, legal and technical layers. For the foreseeable future, however, moderation and banning seem likely to remain the toolbox for social platforms. The empirical work in this paper suggests that when narrowly applied to small, specific groups, banning deviant hate groups can work to reduce and contain the behavior. We would argue that the efficacy of these strategies should inform conversations around their possible future use.