Nowadays human interactions largely take place on social networks, with online users' behavior often falling into a few general typologies or "social roles". Among these, opinion leaders are of crucial importance as they have the ability to spread an idea or opinion on a large scale across the network, with possible tangible consequences in the real world. In this work we extract and characterize the different social roles of users within the Reddit WallStreetBets community, around the time of the GameStop short squeeze of January 2021 -- when a handful of committed users led the whole community to engage in a large and risky financial operation. We identify the profiles of both average users and of relevant outliers, including opinion leaders, using an iterative, semi-supervised classification algorithm, which allows us to discern the characteristics needed to play a particular social role. The key features of opinion leaders are large risky investments and constant updates on a single stock, which allowed them to attract a large following and, in the case of GameStop, ignite the interest of the community. Finally, we observe a substantial change in the behavior and attitude of users after the short squeeze event: no new opinion leaders are found and the community becomes less focused on investments. Overall, this work sheds light on the users' roles and dynamics that led to the GameStop short squeeze, while also suggesting why WallStreetBets no longer wielded such large influence on financial markets, in the aftermath of this event.

翻译：如今，人类互动主要发生在社交网络上，在线用户的行为常可归为若干典型类型或"社会角色"。其中，意见领袖至关重要，因为他们有能力在网络上大规模传播思想或观点，并可能对现实世界产生实质性影响。本研究提取并描述了2021年1月GameStop轧空事件前后——当一小群坚定用户引导整个社区参与大规模高风险金融操作时——Reddit平台WallStreetBets社区用户的不同社会角色。我们采用迭代式半监督分类算法识别普通用户及包括意见领袖在内的相关异常用户画像，从而辨别扮演特定社会角色所需的特征。意见领袖的核心特征在于大规模高风险投资和对单只股票的持续更新，这使他们得以吸引大量追随者，并在GameStop案例中点燃社区兴趣。最后，我们观察到轧空事件后用户行为与态度发生显著变化：未再发现新意见领袖，社区对投资的关注度降低。总体而言，本研究揭示了催生GameStop轧空的用户角色与动态机制，同时解释了为何该事件后WallStreetBets不再对金融市场具有如此巨大的影响力。