Mandatory read for all Nostr users: http://www.skyhunter.com/marcs/petnames/IntroPetNames.html
Marc's S.F. novel is literary fast food but has some of his ideas in it about organizing future society: https://www.amazon.com/Earthweb-Marc-Stiegler/dp/067157809X
Petnames is the only workable system. It should be coupled with a visual indicator of whether the person is familiar to you to prevent spoofing. The equivalent of a blue check for users that I have signed a key for and some other indicator for close degrees of separation.
mark miller told me petnames solve for a) unique names on hash b) findable names on easy human renaming c) available humane-naming verified by non-human computer namespace hash dominic tarr spoken of anyone's public-key as renamable to anything anyone wants, kinda like free speech: rename any hash-name to any human-name you like, just don't expect anyone else to copy
is it made non-mandatory because namecoin now exists? ie. zooko's triangle solved