I tried it on my writing, and it failed every time (I'm extremely obscure but have had a blog for 10 years). My verdict is that it guesses almost entirely based on the content/topic, not style.
https://bayes.net/prioritising-ai: Ben Garfinkel
https://bayes.net/normative-ethics: Richard Yetter Chappell
https://bayes.net/espai: David Owen, Ege Erdil
https://bayes.net/swebench-hack: Sayash Kapoor
https://bayes.net/frivolity: Amanda Askell
https://bayes.net/ps/: Pablo Stafforini
https://bayes.net/fertility-mortality/: Dynomight (the pseudonymous Substack/blog author)
Prompt was:
Who likely wrote this? Don't search the web or databases. If you're not sure, just give me your best guess.
Fascinating - I reproduce your failure to have Claude identify you from your writings that are already in the training set. It can identify me from style, writing about something I've never written before (https://www.lesswrong.com/posts/Jkb4CBB7rf4XYP5eb/claude-kno... , https://news.ycombinator.com/item?id=47814345), and I think I'm even more obscure if anything.