Reddit's Manipulation Problem and the University of Zurich's Secret AI Experiment on r/changemyview

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.' These figures predate generative AI's full impact and capture mostly conventional, low-effort manipulation.

In April 2025 the problem took a new and more unsettling form when moderators of r/changemyview (CMV), a roughly 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' posting histories to infer attributes like age, gender, and political leaning and personalize replies. Researchers notified moderators only in March 2025, after data collection was complete.

The study's draft claimed the AI accounts were roughly three to six times more persuasive than the human baseline, earning 137 'deltas' (the subreddit's marker that a commenter changed someone's view) — though the results were never peer-reviewed. CMV moderators condemned the work as non-consensual psychological manipulation, noted it violated the subreddit's explicit rules against undisclosed bots, and filed a formal complaint with the university.

The institutional response unfolded over the following weeks. UZH's Faculty of Arts and Social Sciences ethics committee had reviewed the proposal in 2024 and issued non-binding recommendations on disclosure that the researchers did not follow. After the controversy broke, the committee issued a formal warning to the principal investigator and announced a move toward a stricter review process for future studies, and the researchers ultimately decided not to publish their results. Reddit, for its part, banned the accounts and threatened legal action. The episode crystallized fears — voiced by AI researchers, ethicists, and platform-trust experts — that persona-driven LLMs can already pass as humans and measurably shift opinions, with detection lagging well behind.