Enhancing Moderation in Decentralized Social Media: A Comprehensive Approach to Community-Level Blocklist Management and Customization on Mastodon

Abstract

Content moderation is critical for maintaining inclusive and civil online communities by deciding on and filtering posted content. While it has been widely studied in centralized social media, moderation practices on decentralized platforms remain underexplored. Community-level blocklists are a key moderation practice among decentralized social media administrators, specifically those running Mastodon, an open-source microblogging software built on the ActivityPub protocol. Blocklists enable moderator collectives to share details of servers of communities worth blocking. However, little is known about how Mastodon moderators perceive and utilize community-level blocklists, and what additional support they may need. To understand this, we conducted (1) content analysis of five popular community-level blocklists and four related moderation tools, and (2) semi-structured interviews with 12 Mastodon moderators. Our content analysis revealed wide variation in blocklist goals, inclusion criteria, and transparency. Interviews showed moderators balance proactive safety, reactive practices, and caution around false positives. They suggested design improvements like comment receipts, category filters, and collaborative voting. We discuss implications for decentralized moderation, emphasizing trade-offs between openness and safety, complex moderator roles, and design strategies for transparency and collaboration.