There are two interpretations rattling around in respect of tacking at a starboard rounding mark. (One has been called "Scurrilous") So here is an attempt to open the discussion - because until there is a World Sailing Call on the subject everything is just opinions.
So the situation:-
Yellow approaches on Starboard, luffs and passes through head to wind before Blue has to alter course. Before Yellow is on a close hauled course Blue has to take avoiding action and protests.
1. Some people think that Yellow should be penalised for infringing rule 13 as the definition says mark room does not include room to tack, unless she is overlapped inside and to windward of the boat required to give mark room (which she is not)
2. Others take the view that having passed head to wind, she is sailing within the mark room to which she is entitled and is therefore exonerated for her breech of 13 (and possibly other rules) by rule 21.
The argument goes that once she is through head to wind she is not tacking, as she will not pass head to wind. The heading of Rule 13 - "While Tacking" is just a heading, it is not repeated within the rule itself so has no relevance. The definition of tacking was removed some time ago (certainly by 1997)
I am pretty certain that I have been instructed by chief umpires to call the situation differently on different weeks. I think that if the sailors get to hear of interpretation 2 then we are going to see a lot more of these situations, as Yellow will feel safer tacking.
Two other circumstances are going to make Umpires unpopular.
The first, and not a new situation, is that while Yellow is on starboard 16.2 applies to her and if she is late with her tack, and Blue is ducking her, the swing of her stern could easily cause Blue to have to make a further alteration of course. Yellow would be penalised if there is a protest and this is the case. Only problem is that if the Umpire is to windward of the mark he probably won't be able to judge the distance between the stern of Yellow and the bow of Blue. The call will be easier if the umpire is following the boats in but opinions are going to differ.
The new situation is that if Blue does duck and become inside boat from clear astern she will be entitled to room, only if the outside boat is able to give it. Much will depend on how far Yellow is from the mark when she tacks and exactly when the overlap is established - plenty of room for different opinions on this one.
And, I think, we also have the instantaneous overlap situation where if Blue is overlapped inside when Yellow passes head to wind she is entitled to room regardless.
As if the windward mark was not complicated enough already.