Recently I had someone track down my real life identity and contact me from forum comments and public information. One comment (aircraft ownership) made me one of a few hundred people on the planet which could be refined by subsequent related comments, first name, gender and digging through multilayered company records gave a 100% identity match and contact information. It took him about two days.
It turned out to not be a bad thing, there was nothing nefarious, we have become friends, but it did point to personal security flaws that have since been rectified.
Proof of my existence.
At the time I was under a continuous months long attack from an analyst (read internet weakling) who found and shared a couple of relationships in a database that his employers were less than pleased to find out about and fabricated "facts" to fit his twisted narrative. I had inadvertently made it so blindingly easy to find my identity, but that didn't serve his purpose.
And to counter I tracked him down and started with a selfie with him in the background... it gets better! :evil