alt Hacker NewsAll that expertise (which requires some proper experience in the topic) even before you plug a llm to it, even few years ago they were good enough to identify unique writing styles of people across different accounts on HN.
Anonymity is gone from internet for some time.
I have seen document-analysis guides with info on how to identify the regional location of anonymous Internet commenters specifically within the US 48 states if you have a sufficiently large corpus of their text, as it relates to how they use certain regional slang, metaphors, colloquialisms, and words to describe things. Think of it as similar to how linguists have made maps showing regional variations in whether people call it "soda" or "coke" or "pop", but extended to all other common forms of North American dialect.
https://www.businessinsider.com/soda-vs-pop-map-2012-7