You "own" your private key, not your notes, nor your images.
You are in control of your keys and what you do with them; you don't have control over what other people do with the content that you signed and published.
Discussion
You don't have control of the event, to the extent that you can't keep them from copying or deleting it, but you can keep them from altering it. Which is mega.
This is, for instance, one reason we want publications as events, so that the content can't be altered.
It's a new possession/ownership dynamic, I think. Difficult to describe with analogies, as it's novel.
There is non-repudiation too, which is also big.
Yes it's novel, that's why we should strive to be careful with our words and analogies. "Owning data" might give the wrong impression, for example.