In my mind, the "Right Thing to Do" would be to follow the precident established by OpenPGP's `.well-known` email-hashing in Web Key Directory (not the prefix of course, and barring technical arguments justifying deviation, which may be considered on merit).
> SHA-1 hashed and z-Base-32 encoded [to distinguish it from a fingerprint]
> The local part is always lower-cased before the encoding. [...] A common example for case-insensitivity are visiting cards which capitalize the canonical lowercase mail address for easier reading.
> https://example.org/.well-known/openpgpkey/hu/XXXX
> SHA-1 hashed and z-Base-32 encoded [to distinguish it from a fingerprint]
> The local part is always lower-cased before the encoding. [...] A common example for case-insensitivity are visiting cards which capitalize the canonical lowercase mail address for easier reading.
https://wiki.gnupg.org/EasyGpg2016/PubkeyDistributionConcept