Owen Xingjian Zhang will present his MSE talk “Enhancing Moderation in Decentralized Social Media: A Comprehensive Approach to Community-Level Blocklist Management and Customization on Mastodon” on Wednesday, April 23, 2025 at 1:30pm in CS 302. The members of his committee are as follows: Andrés Monroy-Hernández (Adviser) and Manoel Horta Ribeiro (reader) All ae welcome to attend. Please see abstract below. Tools such as blocklists serve as crucial mechanisms for managing online interactions by preventing unwanted engagement and mitigating harassment. Most implementations of blocklists operate at the individual-level, where users can independently manage their blocklists. However, prior research suggests that blocklists at the community-level could be more effective, reliable, and particularly valuable for non-dominant groups seeking counterpublics where they can be safe from the systemic abuse they face online. At the same time, research on the use of community-level governance tools on platforms point to substantial challenges that would undermine the usefulness of community-level blocklists. In this work, we look to Mastodon, a decentralized social media network which allows independent servers hosting groups of users to enforce blocklists at the community-level / for the entire server; we aim to understand how community-level blocklists tools can be designed to maximize their expected benefits. Using a mock-up of a community-level blocklist tool interface informed by prior work, we ask: RQ1: What are the common features of community-level blocklists? RQ2: How do moderators perceive and utilize community-level blocklists? RQ3: What design features would enhance the usability and effectiveness of community-level blocklist management tools? Based on our results, we propose design implications to improve transparency, customization, and moderation flexibility in blocklist management tools for decentralized social media networks.