It's going to come down to the judge until we have an exemplified interpretation.
Jake,
I don't really see much difference in opinion about the interpretation of the rules here. I think the arguments are not about the boats' obligations, but about the facts of the incident. If boat(s) didn't keep clear, or give enough room, then one (or both) are being too aggessive. The crux of deciding such a protest is determining which boat that was.
What were the conditions? What was the wind velocity? What was the sea state? What course were the boats on? How fast were they going?
Did the windward boat attempt to pass so close that her own actions made her unable to keep clear? That is, was she too close to respond if L maneuvered? Did she not keep a good lookout? Did she not respond promptly to actions of the leeward boat? Was her boathandling in any way unseamanlike?
What were the actions of the leeward boat? Did she make a hard turn into the windward boat or did she come up gradually? Did she keep a good lookout? Was she attempting simply to defend her wind, or was she trying to trip the other boat? Did she reasonably attempt to avoid contact, damage, and injury?
Now, I'll admit that there's a pretty big gray area there. When the situation is clear one way or the other, then the decision is easy, but otherwise, that's where judgement comes into play. There are differences of opinon between judges as to how much room is enough, and even what level of boathandling qualifies as "seamanlike". At the SAYRA Judges Committee meeting earlier this year, we had an hour-long discussion of what skill level constituted "seamanlike" - without reaching a consensus.
I think we'd all agree that it's better to pass far enough away to avoid that gray area. Dave Perry suggests that a boat closer than two boatlengths of a leeward boat is in jeopardy of not keeping clear. If a boat flying a spinnaker attemps a reaching pass to windward within two boatlengths of a boat not flying one, she should be prepared to douse, or even douse ahead of time. Best of all would be to pass with enough separation that the leeward boat doesn't try to defend against it.
The rules place no burden of proof on either boat. See ISAF Case 50. Protest Committee must find the facts and base their decision them. Therefore, it is critical that you present your facts as clearly and as convincingly as possible.
Regards,
Eric