If |12.l8 13.u6 14.r8 15.u10

OK, David, ask a silly question, get an answer. Sure. after If |12.l8 13.u6 14.r8 your 15.u10 works NOW. But why not |6. r8, which is what I would have played immediately in that position? Would that not have effectively passed by your block at s9? mc.

Yes |6. r8 would have won the local battle and that's what I was expecting, but that doesn't necessarily mean it was black's best move. My plan was to continue 7.s14 and then for example 8.s6 9.k9 and white has threats to connect K9 to the top and to the bottom. My s9 was a trick I learned from playing the bot. It's a tempo threat to improve my connection to the bottom, and that helps my K9 peg. You have the entire board before you. Why not use it? IMO a good move 6 for black would be, oh I dunno maybe |6.q15 The opening is the most difficult phase. You don't always have to respond locally to whatever the opponent is doing. It's usually better to spread your pegs in a direction parallel to your own border rows, to generate your own threats.

Actually |6.r8 7.s14 8.s6 9.k9 doesn't look so good after 10.l5 but 9.j8 looks better.

And it's not a silly question, it's an important question.