Aside from the "statement" it makes, I think it is useful to identify responses that a resource provider might like to make but is not permitted to make (i.e. c

Aside from the "statement" it makes, I think it is useful to identify responses that a resource provider might like to make but is not permitted to make (i.e. censorship). Given the prevalence (editorial: "enormity") of censorship problems -- both current and pending -- being able to distinguish between them and other failures provides actionable information on a useful scale and frequency. The particular response code proposed does make an elegantly concise and culturally cognizant statement -- something that RFC's are not entirely unknown for. The proposal is both practical and well-put, IMHO.