(Forking from the discussion in T4728 (which resulted in the Realname field becoming optional)...)
Being able to //change// the string from "Real name", would be very helpful. That way sites can instruct their users to use whatever they prefer.
E.g. At Wikimedia's installation, it would be nice to have the field ask users for "//Additional name//", or "//Also known as (e.g. real name or IRC nickname)//".
We don't want to just hide the field entirely, because it's a useful way for getting alternate autocomplete search-strings in, for CCing/Mentioning people. (Because there's always that one user, who uses an IRC nickname that differs from their username and realname and emailaddress-prefix...)