Social media platforms employ various content moderation techniques to remove harmful, offensive, and hate speech content. The moderation level varies across platforms; even over time, it can evolve in a platform. For example, Parler, a fringe social media platform popular among conservative users, was known to have the least restrictive moderation policies, claiming to have open discussion spaces for their users. However, after linking the 2021 US Capitol Riots and the activity of some groups on Parler, such as QAnon and Proud Boys, on January 12, 2021, Parler was removed from the Apple and Google App Store and suspended from Amazon Cloud hosting service. Parler would have to modify their moderation policies to return to these online stores. After a month of downtime, Parler was back online with a new set of user guidelines, which reflected stricter content moderation, especially regarding the \emph{hate speech} policy. In this paper, we studied the moderation changes performed by Parler and their effect on the toxicity of its content. We collected a large longitudinal Parler dataset with 17M parleys from 432K active users from February 2021 to January 2022, after its return to the Internet and App Store. To the best of our knowledge, this is the first study investigating the effectiveness of content moderation techniques using data-driven approaches and also the first Parler dataset after its brief hiatus. Our quasi-experimental time series analysis indicates that after the change in Parler's moderation, the severe forms of toxicity (above a threshold of 0.5) immediately decreased and sustained. In contrast, the trend did not change for less severe threats and insults (a threshold between 0.5 - 0.7). Finally, we found an increase in the factuality of the news sites being shared, as well as a decrease in the number of conspiracy or pseudoscience sources being shared.

翻译：社交媒体平台采用多种内容审核技术以移除有害、攻击性和仇恨言论内容。各平台的审核力度各不相同；即使在同一平台内，审核标准也可能随时间演变。例如，Parler作为一个在保守派用户中流行的边缘社交媒体平台，曾以最宽松的审核政策著称，声称为其用户提供开放的讨论空间。然而，在2021年1月12日将2021年美国国会大厦暴动与Parler上部分团体（如QAnon和Proud Boys）的活动关联后，Parler被苹果和谷歌应用商店下架，并暂停了亚马逊云托管服务。Parler必须修改其审核政策才能重新上架这些在线商店。经历一个月的停运后，Parler以一套新的用户准则重新上线，体现了更严格的内容审核，尤其是在\"仇恨言论\"政策方面。本文研究了Parler实施的审核变化及其对内容毒性程度的影响。我们收集了Parler自2021年2月至2022年1月重新上线应用商店后的长期纵向数据集，包含来自43.2万活跃用户的1700万条帖子。据我们所知，这是首次采用数据驱动方法研究内容审核技术有效性的工作，也是Parler短暂停运后的首个数据集。我们的准实验时间序列分析表明：Parler审核变化后，严重毒性内容（阈值超过0.5）立即减少并持续保持；而对中低威胁和侮辱性内容（阈值介于0.5-0.7之间）的趋势则未发生变化。最后，我们发现所分享新闻网站的事实性有所提升，同时阴谋论或伪科学来源的分享数量有所下降。