@Gordon Davies wrote:
Every boat of an ISAF International Class and Recognised Class shall carry on her spinnaker a sail number and, at international events, national letters denoting her national authority.
Correct, but if you read on in those rules you will find an exception; National letters may be omitted if an international numbering schema exists. The best known example is the Laser class that generally does not use National letters. Since the Wayfarer class uses international numbering it has always been my understanding that national letters were optional in our class.
Having discussed this matter on several occasions, most people I spoke to felt that it would be better to omit the national letters to emphasize we are an International bunch of sailing friends, and Nationality plays only a minor role. As a consequence all our Nationals are Open Nationals as you may have noticed and there are many International get-togethers every year.