there will be so many redundant caches that deletion is pretty much nonsensical on nostr. you can of course try your best but the idea of the note disappearing from every nostr database cache is a pipe dream.
every damus client has a copy... what happens to the caches that are backed up and don't get the delete request. the data is still there.
Clients should request deletion events from the author of each note and if there is one, hide the note content in the client and indicate that the author has requested the deletion of this note.