Reddit's Manipulation Problem and the University of Zurich's Secret AI Experiment on r/changemyview
April 2025
Reddit's own transparency reports document persistent spam and inauthentic-account activity. The problem moved from anonymous spammers to credentialed academics in 2025, when University of Zurich researchers secretly ran AI bots posing as real people in r/changemyview to test machine persuasion without users' consent.
What happened
Vote manipulation, spam, coordinated inauthentic behavior, and astroturfing are recurring problems on Reddit, and the company's own data confirms their scale. In Reddit's official Transparency Report for January to June 2024, the platform reported redditors shared over 5.3 billion pieces of content, of which administrators and moderators removed just over 3%; of admin removals, spam accounted for about 66.5%, with a smaller share categorized as 'content manipulation.'
In April 2025 the problem took a new form when moderators of r/changemyview (CMV), a ~3.8-million-member debate community, revealed that researchers from the University of Zurich (UZH) had secretly deployed AI-driven accounts. The data-collection phase ran from November 2024 to March 2025, during which the bots posted 1,783 comments using fabricated personas — including a sexual assault survivor, a trauma counselor, and a 'Black man opposed to Black Lives Matter.' A separate AI analyzed targeted users' histories to personalize replies. Researchers notified moderators only in March 2025, after data collection was complete.
The study claimed the AI accounts were roughly three to six times more persuasive than the human baseline, earning 137 'deltas.' CMV moderators condemned the work as non-consensual psychological manipulation, noted it violated the subreddit's rules against undisclosed bots, and filed a complaint. The university's ethics committee had made non-binding recommendations in 2024 that were not followed regarding disclosure; it later issued a formal warning and the researchers decided not to publish.
Impact
The episode became a landmark case in research-ethics and platform-trust debates, demonstrating that undisclosed AI agents could pass as humans, build credibility through invented trauma narratives, and measurably shift opinions in a community built for good-faith human debate. It sharpened concerns that personalized, persona-driven LLM persuasion at scale could be weaponized for political astroturfing or influence operations, and that bot-detection lags behind. It also reinforced fears about the erosion of trust in user-generated content as AI text becomes harder to distinguish from genuine human posts.