We have to reuse item fields in ways they were not intended to quite often in order to respond to libraries specific demands. In some cases we will control these fields with an authorized value, but not all fields will display the authorized value description on the opac and admin interface. See: http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=7379 Which took care of this problem for the copynumber field.
Here's a proposal for solving this problem : The table in which items are displayed on the additems.pl actually lists all the information properly, with the description and not the code when a field is linked to an authorized value. This also has the added benefit of displaying whatever is found in more_subfields_xml with the right title for the column, which would denifitely solve the problem of recyvling fields.
The bug description is not clear on which fields should be fixed. I am wondering if this is a WONTFIX as arbitrary reuse of fields probably is causing other issues as well and improving more_subfields_xml instead might be the better idea.
Closing as WONTFIX as per my suggestion from 2019, please reopen with more information if you disagree!