Forum OpenACS Development: How to delete message keys from the translation server

I just found four message keys in file storage that are no longer in use: http://translate.openacs.org/acs-lang/admin/message-list?package%5fkey=file%2dstorage&locale=de%5fDE&show=untranslated

I'm wondering now how we could get them deleted from the translation server and the catalog files. Furthermore, is there a general way to detect which message keys are still in use (except using grep)?

Or do we say we don't care about nominal members?