Date: Thursday, November 12, 2025
Speaker: Alexios Mantzarlis
Title: The surprising resilience and uncertain future of Community Notes on X
Abstract: Community Notes are emerging as an important feature of content moderation on major platforms. This approach uses a bridging algorithm to identify user-generated context with upvotes across political divides - supposedly spinning consensual gold from partisan straw. First launched on X, similar programs have now launched on Meta platforms, TikTok, and YouTube. But what drives people to contribute corrective information that is more likely than not never to be seen for a private platform owned by a mercurial billionaire? I will refer to extant literature before presenting anecdotal findings from my reporting on super contributors as well as a new regression discontinuity design analysis that sheds some light on the positive effect of having a note published. I will then look at what we still need to learn about crowdsourced context generation on social media.
Bio: Alexios Mantzarlis joined Cornell Tech in May 2024 as the inaugural director of the Security, Trust, and Safety Initiative (SETS), which strives to mitigate and prevent digital harm through graduate education, active communities of practice, and research.
Mantzarlis joined Cornell Tech from Google, where he created the adversarial red team focusing on content risks from generative AI and managed a team responsible for Google Search’s content policy on factual accuracy and high promise answers. Mantzarlis was previously the founding director of the International Fact-Checking Network (IFCN), where he helped draft the fact-checkers’ code of principles and shepherded a seminal partnership between fact-checkers and Facebook.
Mantzarlis holds a BA in philosophy, politics and economics from the University of York, an MA in European affairs from the Institut d’Etudes Politiques de Paris and an MSc in economics and management from Università Bocconi in Milan. He is Greek-Italian and bikes to work from Long Island City, where he lives with his awesome wife and daughter.
