Oh for goodness sake!
1) No
2) Of course if my unit is not on the addressee list, the plan wont appear, but that is a matter for the person submitting the plan, not the addressee.
3) I normally only mark Cat A or B Flts in box M. Do you?
4) No as an abbreviated flight plan only pertains to a portion of a particular flight.
The topic of flight categories was originally posted to clarify that priorities do have a bearing on how an ATCO does his job, and that it not just a case of the "big boys" getting priority over GA an training traffic because of the thought and biases of an ATCO.
If anyone else has a problem with flight categories or Air Traffic Standards, may I suggest you submit them directly to the Safety Regulation Group at CAA House.