I have also used "stories" for things like this, and I make sure to include the name of the person in the title (so it will show up in searches, and maybe get pushed as a hint), as I think things have a better chance that way.
But - the sad truth is that several times I have noted that my "story" about something had been attached to someone's tree, so I go to the tree to see what they have and . . . you guessed it . . . they attached the story that says why X is untrue, yet their tree still says that X is a fact (meaning that either they didn't even read what I wrote, which I think is likely, or they read it and didn't care, or read it and didn't understand it but didn't bother to ask about it, or, or, or . . .)
You may get more of a reaction if you start posting comments on the person's tree, explaining why something is a mistake. It's true they can delete them, but maybe at least someone else will see it and be headed off from a mistake.