Users currently can in the UI make arbitrary changes to a plugin configuration including the deletion of lines in a listofX. Currently each and every plugin needs to check by itself what may have changed and how to deal with it. The plugin's task would be much easier if in addition to the full configuration, the server would also send a diff so that it would e.g. be possible to see if an entry in a list was removed etc.
per BZ triage ... crouch, loleary, foley