Social media's role in the spread and evolution of extremism is a focus of intense study. Online extremists have been involved in the spread of online hate, mis/disinformation, and real-world violence. However, the overwhelming majority of existing work has focused on right-wing extremism. In this paper, we perform a first of its kind large-scale, data-driven study exploring left-wing extremism. We focus on "tankies," a left-wing community that first arose in the 1950s in support of hardline actions of the USSR and has evolved to support what they call "actually existing socialist countries," e.g., CCP run China, the USSR, former soviet countries, and North Korea. We collect 1.3M posts from 53K authors from tankies subreddits, and explore the position of tankies within the broader far-left community on Reddit. Among other things, we find that tankies are clearly on the periphery of the larger far-left community. When examining the contents of posts, we find misalignments and conceptual homomorphisms that confirm the description of tankies in the theoretical work. We also discover that tankies focus more on state-level political events rather than social issues in comparison to other far-left communities. Finally, we show that tankies exhibit some of the same worrying behaviors as right-wing extremists, e.g., relatively high toxicity and an organized response to deplatforming events.

翻译：社交媒体在极端主义传播与演变中的角色一直是研究热点。在线极端分子参与网络仇恨、虚假/误导信息传播以及现实暴力事件，然而现有研究绝大多数聚焦于右翼极端主义。本文首次开展大规模数据驱动研究，系统探讨左翼极端主义现象。我们聚焦"坦克党"——这一兴起于20世纪50年代、支持苏联强硬路线的左翼社群，现已演化为拥护其所谓"实际存在的社会主义国家"（如中国共产党领导的中国、苏联、前苏联国家及朝鲜）的群体。通过收集来自坦克党子论坛的53K名作者的130万条帖文，我们探究该群体在Reddit平台更广泛极左社群中的定位。研究发现：坦克党明确处于极左社群边缘；帖文内容分析揭示的理论描述失谐现象与概念同构性，印证了相关理论论述；相较于其他极左社群，坦克党更关注国家层面政治事件而非社会议题。最终结果表明，坦克党展现出与右翼极端分子相似的令人担忧的行为特征，如相对较高的言辞毒性及对平台去平台化事件的有组织应对。