Thank you:)
Discussion
I changed nostr.json?name=user not found error code to 418 so CF doesn't cache it. But maybe it should return code 200 with empty {"names":{}}? I wonder how others do it.
If you register a username on iris.to and later on change your NIP-05 address then the previously registered username becomes available again?
Looks like it can't be changed.
You can use the username as a short link to your profile outside of Nostr: iris.to/mattoso
NIP05 is just extra feature of the username. You can use it or use some other NIP05 if you have many.
I ask because I created a username on iris and then changed the NIP-05 address on my profile and my previously registered iris.to/username was said to be "available" when I opened iris.to from a "new" browser and tried to register it again with a "new" private key.