1. The problem has long been the definition of an obstruction.
Even a boat half a mile away (or back at the dock) is "an object that a boat could not pass without changing course substantially ... if she were one boat length away from it."
2. If Blue held her course, she would pass close behind Yellow. So Yellow is not an obstruction to Blue's travel in the normal definition.
The same may be true of Green - perhaps closer.
3. As the scenario progressed Yellow became the outside boat required to give room to Blue, which she did. And Blue chose to gybe away.
4. Also:
19.2 says the right of way boat MAY choose to pass - not SHALL choose.
In this instance ROW Blue chose not to pass Yellow, so she had no obligation to give room to Green.
5. No rules were violated.

Ang -

I'm inclined to agree with you. Now we PROs are faced with how do we catch the perpetrators fairly. This technique is pretty common and hard to see from the ends of the line. Of course, a fouled boat could protest. 

"If the details included remove any ambiguity about which incident the delivered protest is referring to"
Clear as mud.
Does not answer the question.

Ben,
Safety is rule 1 and 14 obligates boats to avoid contact or not to cause contact. There was reasonable apprehension in the mind of ROW boat that there may be a collision and she took action to avoid that situation. In my opinion, I will DSQ KC boat.

Yes we've used W finishes for many fleet events.  It works well for the back of the fleet. Not entirely sure the front of the fleet would be thrilled at having it used if they weren't 100% sure they were being recorded at the front.

I realise handicap racing is not popular on this board. For reference - W finishes are not appropriate in handicap races as you need to adjust time and 'distance' (laps).