It appears to largely be able to identify people who are prolific public writers. I just asked it to identify a whole bunch of comments I've made on private Discord servers and it said it couldn't for all of them, even when they had details that would identify me uniquely to anyone who knows me well enough (work locations, city I live in, wife's employer, my employer).

All the people it seems to be identifying are bloggers, journalists, and/or published authors.