@Mtt @manton Given the Notes feature's focus on encryption and privacy, I would recommend against introducing extra metadata like this. Not everyone might want the world to know that they previously had a note published at a certain URL. For plausible deniability.
If Micro.blog leaks the information "there was a private note at this URL in the past" – attackers and bullies might exploit that in different ways. For example, a bully that wants to perform a character assassination on a blogger could author a nefarious post like "Hey, I just read Joe's note here (since deleted) where he wrote [insert false statement here]." and link to a deleted note that actually said something entirely different. If Micro.blog were to leak that there actually was a private note there in the past, it would add credibility to the bully's post.
There might be other scenarios where an attacker could be helped by knowing a note existed in the past. Generally, you want to leak as little metadata as possible when dealing with secrets and semi-secrets.