This is probably the time to add some invitation system like GMail had in the beginning. Or make a shade for accounts <1yr. Or something else, before things get too mixed.

I just took a look at /noobcomments and wow, there's ever a comment where a person argues with AI instead of, you know, using their own brain. It was abivous it was ai since it was formatted with markdown

I wanted to point out that em dashes are autocompleted by the iOS keyboard. So the false positives and true negatives might have some overlaps without more details. I think a better indicator would be to only detect em dashes with preceding and following whitespace characters, and general unicode usage of that user.

Additionally, lots of Chinese and Russian keyboard tools use the em dash as well, when they're switching to the alternative (en-US) layout overlay.

There's also the Chinese idiom symbol in UTF8 which gets used as a dot by those users a lot, so that could be a nice indicator for legit human users.

edit: lol @ downvotes. Must have hit a vulnerable spot, huh?