I have LDAP authorization configured and correctly working on my Jenkins installation.
However, when the value of parameter 'fullName' is to be changed (i.e., by changing the user display name in the LDAP, or by changing LDAP Plugin parameter 'displayNameAttributeName' (my case), the fullName field in the file "$JENKINS_HOME/users/.../config.xml" is unchanged.

I do not know if this is the LDAP plugin problem or the global Jenkins problem, but the problem exists in my environment.