I can't believe that anyone reading Case 78 would remain in any doubt.

Was there some more background?

Did you invite your correspondent to:

What did the enquirer mean by 'match racing tactics'?

I can't recognise any match racing tactics in the scenario.

I agree with Randy.

A stuck her head in the noose by creating a windward overlap by bearing away across B, forfeiting her initial RRS 15 protection.  She then regained protection when B changed course.

Nothing in the fleet racing or match racing rules says that B is required to make it easy for A to keep clear.

Why did A take penalty turns?

Because she didn't understand how RRS 16/43.1 works?

Nothing in the fleet racing rules says that competitors who don't understand the rules should get special treatment.

  John Chrisman mentioned case B3 in The Call Book for Radio Sailing, that talks about a boat "unbreaking" rule 16.1.  That is a very interesting case as rule 18.3 doesn't apply because P never completes her tack.   
The term 'unbreaking' is not helpful. A boat may comply with RRS16.1 by changing course a second time to give the other boat room to keep clear - see, for example TR Call B4, or D3, in which a RoW boat changes course to comply with RRS15.
In RS Call B3 RRS 18.3 does apply because P has passed head to wind from port to starboard and S was fetching the mark on starboard since entering the zone. However, RRS 18.3 never comes in to play in this incident, except that it means that P, who becomes inside boat, when she passes head to wind,, is not entitled to mark room. At 2 P is in a position to keep clear by tacking. As she is luffing to head to wind and passing head to wind S changes course and is now on a collision/converging course. P manoeuvres promptly in a seamanlike way by continuing to bear away. S is required to give P room to keep clear, which includes room not to touch the mark. In B3 question 3, S complies with RRS 16.1 by luffung to give P room to keep clear.

Diego - yes, I get that in match and team racing part of the game is allowing the boats to get closer together than you would in fleet racing.  For fleet racing WS Case 103 helps us understand 'in a seamanlike way'

CASE 103
Definitions, Room
The phrase ‘seamanlike way’ in the definition Room refers to boat-handling that can reasonably be expected from a competent, but not expert, crew of the appropriate number for the boat.

But I'm not sure how this changes things other than to say that P breaks rule 10 earlier in the scenario, possibly at position 1.

Hi all,

Ric of course, thank you very much. I updated the fix. Spinning the boats fast should be now with expected result.

Next step in development will be a feature to record step by step movements, and be able to share this without login.

Best

There's this *amazing* website that has little pop-up case references next to each rule, with a helpful summary of the points therein. It references the Judging manual too sometimes. There's a small fee but well worth it for the functionality, as well as being able to deliver regattas on it.  It's called racingrulesofsailing.org ;-) 

Seriously - I use that as reference for all the WS cases. Of course, back to the original publications for definitive text but as a quick-reference it's invaluable. It directs you to the relevant case rather than reading all the cases and trying to backsolve for a given incident.