I actually have a similar story I was waiting for another Friday to share but it's on point now.
My late stepfather was estranged from his father & somewhat from his mother, so it's been a challenge to build his tree. I did add notes to her profile, and some time ago, another curator was able to match his father's side to a MyHeritage tree; it's just been hard to verify with name changes and what not.
A few weeks ago the grandson of her second partner tracked me down based on those same notes. Unfortunately I couldn't help them with photos from his childhood, but they did give me permission to port over whatever I wanted from their ancestry.com tree to Geni.
It's some tree! By adding a little more research they didn't make explicit in theirs (but aren't hiding, either) I now have a much better idea of life in NYC "bootleg liquor" 1930s.
And .. I'm now connected to the enormous French Canadian tree on Geni.
Because of two lines of notes in a public, long deceased profile.