It's something I have suggested before, but didn't get traction.

I actually still think it should be implemented. JSONs must stay compliant. Other than that, I don't care much how the implementation happens, as long as it does.

One issue one might raise is performance. However, this is only a concern if clients load and verify NIP-05 identities for every account every time it's displayed. And the only real reason for doing so is the checkmark, which shouldn't be there anyways.

I think "verification" should happen, for all domains, when the user actually checks the info page of an account, which wouldn't actually require much.