It probably means that your writing stylistically is close to the vector-space average of "good" writing, which is what AI produces.

FWIW, your comment history here does not look like AI at all to me, and I think I have a very (maybe too?) high sensitivity to AI slop.

I haven't tried my HN comments; I've only tried things spanning more than a few sentences and that I've put more effort into. I only discovered this when my son put an e-mail I wrote to his teacher that he was CC'd on into the tool on his school iPad.