@Elizafox @Gargron Delete functionality for profiles ought to be _profile_ deletion as suggested in that thread. It would be up to each federated remote instance whether to delete the profile and/or data.
The possibility to delete an account's data should be obvious. But essentially that could be accomplished by just having the user edit their profile data, deleting avatar removing the given e-mail address and such.
Given that the user can already do all those things (I assume in #Mastodon too), I don't see any point in rushing a "profile delete" functionality.
This discussion is also relevant to !fediverse and !GNUsocial (where delete functionality is disabled by default due to account hackability and no delay in deletion).