On the Effects of Decentralized Moderation on Network Robustness and Information Diffusion in Mastodon

2026-06-25

AI Summary

This study investigates how decentralized moderation decisions—specifically, server-level blocking policies in the Mastodon federated social network—affect global network structure and information diffusion. By constructing a signed directed temporal network that integrates follow and block relationships, and employing a hybrid contagion model combining simple and complex diffusion mechanisms, the research leverages signed network modeling, temporal graph analysis, and Markov equilibrium validation to reveal the macrostructural stability of decentralized content moderation. The findings indicate that instances dominated by a minority of active moderators exhibit greater efficiency and resilience in information propagation. While moderation effectively isolates policy-violating content, it simultaneously intensifies echo chamber effects across the network.

Abstract

Decentralized online social networks such as Mastodon distribute moderation power across thousands of independently governed servers, raising fundamental questions about how local block decisions shape global structure and information flow. In this paper, we analyze Mastodon at the instance level by constructing a signed, directed, temporal network in which positive edges aggregate inter-instance follow relationships and negative edges encode daily block actions. Using one year of data, we show that despite continuous moderation activity and changing roles among instances, the network exhibits strong structural stability: signed dyadic motifs and degree distributions display highly persistent dynamics, and aggregated transition matrices satisfy Markovian equilibrium conditions over intermediate time scales. Building on the marked asymmetry between instances that predominantly issue bans and those that are mostly banned, we then study information diffusion on the positive network via a hybrid contagion model that combines simple contagion within groups and complex contagion across groups. We find that information originating in the minority of moderating instances spreads more efficiently, both internally and toward the majority, while the opposite direction is fragile and sensitive to contagion parameters. Echo-chamber effects emerge even in a globally balanced signed network and become stronger under stricter contagion conditions. Together, these results show that decentralized moderation in Mastodon generates a stable macroscopic configuration that both structures and constrains information exchange, effectively isolating norm-violating domains without centralized control.

Problem

• decentralized moderation
• network robustness
• information diffusion
• Mastodon
• signed network

Innovation

• decentralized moderation
• signed network
• information diffusion
• hybrid contagion model
• structural stability