I remember a really impressive demo where someone found all the alt accounts of a HN user using stylometry: https://news.ycombinator.com/item?id=17944484 The account didn't have that many comments on it (maybe ~1000 karma)

He also claims to have used the same algorithm for identifying company insiders for trades (see parent comment in that thread for context).

I don't think he was bullshitting even though his tool isn't public because he has a different NLP project that works reasonably well (https://hnprofile.com/ which can find users based on their interests).