I interpret kind 2 to say "Hey this is a great relay, you guys should try it", rather than "If you want to find my posts in the future, I expect to be putting them here". kind-2 also only has a single relay in the contents.
kind 10001 in nip 23 (pr 32) would work. I'm not excited about parsing the runes language, but it would serve.
Currently gossip does excessively complex tracking of stuff because "here is where I post" information is not easily and widely available.
One idea: on initialization, clients try to open up websockets to a collection of relays. whichever ones successfully establish a connection are published as a parametrized replaceable event with a fixed Kind "K", with "d" tags equal to the URL of the relay. These events ideally would be "sprayed".
Then, as another user, I could query for kind "K" authored by the user I am interested and get the list of relays, with timestamps, they have connected to. By filtering the query I can get the most recent relays, etc.
Obvious privacy concerns. But a good client could prompt user before sending (i.e., "let people know you were using relay wss://XXX"?), and maybe you could set to not send such updates for certain relays.. etc..
Interesting. This allows people to move around rapidly. However, what if I want someone's events spanning a longer time period?
It's the same problem of following threads across multiple relays which isn't fully solved either.
