  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.
