Tom said Consider a starboard tacker waving across a port tacker and potentially ducking for tactical reasons. Technically, P has broken 10; 

.If Starboard waves across port and does not duck Port has not broken a rule. If Starboard waves Port across then as soon as they start to duck have they not assumed a responsibility under 16.1 to give Port room to keep clear? So in that situation isn't there at most a very narrow window in which Port breaks 10? Is there an argument that at all times Port was clear, even if it was by the co-operation of Starboard?

It seems to me that the Starboard boat is altering course early, choosing to pass behind port for strategic reasons, and adding a verbal comment to make her intentions clear.* Indeed I often waive people across who are already clearing me so that they can sail fast, and avoid choking and fouling and screwing me up.

Matt If the waves were coming in at a size to do that from a normal direction then:1.  No-one should be racing.

You mean like this?

Ang I as well .. was just trying to clearly describe where/how the ambiguity resides that you pointed out. 

(Why do I suddenly feel like I'm Charlie Brown and you're Lucy holding the ball! <g>).