I had assumed the triangled cut was the only move, as did Black (Kuroda Yukio) who said he planned to play A next. But - my first chuckle - he said he too was "gobsmacked" when he saw what White played, as follows:



This momentum-denying move is surprisingly effective, especially bearing in mind he has to try to counter Black's sanrensei influence on the right. The game continued in predictable enough fashion to reach the position shown below, where White sanguinely let Black live by cutting off three stones - my second (wry) chuckle given a concurrent thread which involved a debatable capture of three stones.



White went on to win this game rather soon, and his outside wall certainly looks impressive. But it's an interesting question as to how it compares with Black's structure on the right, which is obviously wide open but is backed by the edges of the board.

The sword-wielding method of estimation for White doesn't seem to apply here as there is no obvious extension, so if we instead use the "three points per wall stone" heuristic (which I find slightly optimistic) we get a White value of at least a bit over 40 points. Let us assume the Black stone at the top is cancelled out not just by White's thickness but by White's obvious lead on the left side. We can then estimate Black's moyo very simply by the virtual territory method (i.e. he gets half and White decimates the other half). That looks like something in the region of only 30 points (not to mention at least a couple of points wherever White lives there - no komi, though).

Any other views on the comparison?