Understanding Community-Level Blocklists in Decentralized Social Media

2025-06-05

AI Summary

This study investigates the practice logic, governance tensions, and design requirements of community-level blocking—implemented via the ActivityPub protocol—in the decentralized social platform Mastodon. Through content analysis and in-depth interviews with 12 community moderators, we systematically identify three key trade-offs: (1) heterogeneous blocking targets, (2) tension between proactive safety measures and reactive enforcement, and (3) non-negligible risks of overblocking. We further find that current blocking mechanisms lack critical capabilities—including categorized filtering, collaborative decision-making, and feedback loops. Our contributions are threefold: (1) the first qualitative analytical framework for community-level blocking practices; (2) three actionable interaction design proposals—comment receipts, tiered filtering, and collaborative voting—to enhance transparency and accountability; and (3) empirically grounded insights and operational pathways for decentralized content governance.

Technology Category

• Multiagent Systems: Mechanism Design
• Application Domains: Humanities & Computational Social Science
• Data Mining & Knowledge Management: Graph Mining, Social Network Analysis & Community

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Decentralized Web and Fediverse systems
• Social Networks and Social Media: Media and governance, opinion dynamics, filter bubbles, polarization
• Security and Privacy: Blockchains and distributed ledgers

Abstract

Community-level blocklists are key to content moderation practices in decentralized social media. These blocklists enable moderators to prevent other communities, such as those acting in bad faith, from interacting with their own -- and, if shared publicly, warn others about communities worth blocking. Prior work has examined blocklists in centralized social media, noting their potential for collective moderation outcomes, but has focused on blocklists as individual-level tools. To understand how moderators perceive and utilize community-level blocklists and what additional support they may need, we examine social media communities running Mastodon, an open-source microblogging software built on the ActivityPub protocol. We conducted (1) content analysis of the community-level blocklist ecosystem, and (2) semi-structured interviews with twelve 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 when using blocklists for moderation. They noted challenges and limitations in current blocklist use, suggesting design improvements like comment receipts, category filters, and collaborative voting. We discuss implications for decentralized content moderation, highlighting trade-offs between openness, safety, and nuance; the complexity of moderator roles; and opportunities for future design.

Problem

• Understanding moderators' use of community-level blocklists in decentralized social media
• Exploring challenges and limitations in current blocklist utilization
• Proposing design improvements for decentralized content moderation tools

Innovation

• Analyzing Mastodon community-level blocklists ecosystem
• Interviewing moderators on blocklist usage challenges
• Proposing design improvements for decentralized moderation