Is it safe to assume that keys which only exist in the language.ini, meaning they don't exist anywhere in the php files, are unsused keys/strings?
Example: COM_VIRTUEMART_PLEASE_SEL_ITEM is listed in the BE language file, but doesn't seem to exist in any other file.
dont delete this keys.
We use a keystem for generic messages, like category saved, product saved and things like this.... So you cant find the strings in the php files, because they are concatenated.
For more detailed explanation, look here: http://dev.virtuemart.net/projects/virtuemart/wiki/Writing_translation "What you have to know and to consider"
Of course when you considered that, then we are happy, when you delete unused keys