it can be any note, not just nip78.
nip44 by itself doesn't give you public data that is unlinked to you
Discussion
also the contents are optionally a rumor like giftwraps
better way to describe it is simpler, less DoS-able, and more private nip59 (no p tag) but for your own notes
this should also replace all encrypted versions of NIPs (like lists) that are encrypted to yourself. this is a much better way to do that, assuming you're ok with negetropy-sync-like workflows with private local relays for querying the unwrapped notes locally.
I see now, I missed the derived PNS keypair. So I know what to fetch, but no other user (relay maybe can?) can make a relationship between this encrypted data and myself.
I like that.
Oh, can you add one or two test cases of derived PNS keypairs? I like to make sure to test against those and ensure compatibility.