@614aee83d7eaffc7bc6bbf02feda0cc53e7f97eeceac08a897c4cea3c023b804 Perhaps NIP-42 should be required to send an event matching the identity you authenticated with (except deletions): https://github.com/nostr-protocol/nips/blob/master/42.md
This fixes the “DM events being visible” problem btw. But I don’t think strfry supports it yet.