> Stylometry. Seems like it currently leaves enough textual clues that simple BERT like models have no trouble picking them up, no watermarks needed.

Demo: https://huggingface.co/openai-detector - note it not was not even finetuned to GPT3/ChatGPT, but merely GPT2 (3 years old and much smaller model)

But then I don't know why I'm telling you - when I enter the above text it says it's 99.86% fake, based on 80 tokens :/