Can LLMs Shape Online Discourse? Evidence from a Viral AI Generated Narrative

Current AI safety paradigms assess model outputs in isolation rather than in live social environments. We examine this gap through a case study in which a GPT-4o-generated narrative was deployed to the r/AmITheAsshole subreddit, where it achieved viral reach, elicited a predictable distribution of moral judgements and remained undetected as AI-generated. To characterise the risks posed by this capability, we introduce Plausibility, Propagation and Polarisation (PPP) as analytical dimensions for ecosystem-level influence, capturing authenticity, algorithmic amplification and engagement through moral framing. Our findings suggest that LLMs have implicitly learned structural features that drive human response, a dual-use vulnerability that current evaluation methodologies are not equipped to detect.