I take my bw key with me wherever I go, by boat, car, bike or shank's pony. Do I also need a pair of swinging cork balls to avoid interrogation by the poopee patrol?
I also have a radar key, being a gentleman of a certain age, when I gotta go, I gotta go.
Personally I have no issue with anyone using the facilities as long as they leave them clean and tidy. The extra flush is hardly likely to wear out the porcelain. Imho any horrendously clarted up facilities I've encountered have been caused by careless boaters.