Some libraries would like to choose which fields patrons can modify (or suggest modifications to) through the OPAC when they go into their online account and "my personal information" (for example phone number and email only). This could be a syspref, something like OPACPatronDetailsFields where administrators can put a list of fields, separated by |, which the users can modifiy through the OPAC. If left empty, defaults to everything.
I think what you want is PatronSelfModificationBorrowerUnwantedField, which appears to be incorrectly grouped with Self Registration preferences. Hopefully someone can fact-check me on that.
Oh, you're absolutely right! I didn't even check in the SelfRegistration section since this function is not enabled in this particular instance. Sorry about that! Caroline