Addressable events have a kind in the 30000-39999 range and a d-tag and an a tag that looks like
["a", "<kind>:<pubkey>:<d-tag>", "<relay hint>"]
Indexes allow you to determine the order in which the content appears, but you also just show most-recent first.
I don't know, if that answers your question.
Simpler and cleaner than key delegation is to have a shared key, like we have for nostr:nprofile1qys8wumn8ghj7mn0wd68ytn9d9h82mny0fmkzmn6d9njuumsv93k2tcprdmhxue69uhhg6r9vehhyetnwshxummnw3erztnrdakj7qpqs3ht77dq4zqnya8vjun5jp3p44pr794ru36d0ltxu65chljw8xjqxqf9se , and use that for the index.
