Calvin I don't think completely removes the aji of the cut at b, so I'm thinking that even if white defends solidly with , black still has to come back with something like close like and the / exhange is not necessary. Thoughts?
nachtrabe: Why do you think is a mistake? It looks like a continuation to me. It may be small depending on the rest of the board) but I'm not sure there is a "punishment" per se. in the second diagram also seems over-concentrated to me (jeongseok would be c in the first diagram if black hadn't played , and so I'm not sure how forces a closer play than c).
Dave: If the marked stone does not remove the aji of the cut, what is the aji after 1-10? I think the aji is gone. The refutation of the marked black stone can not be the passive connection by White I think.
Bill: Generally I think is fine. If , and White has played on both sides. Also, Black is overconcentrated. Instead of if Black plays a pincer at, say, a, White has room to extend to b.
Dave: White does not have to "punish" Black. The punishment seems to be included in the original play. There is no meaningful follow up for Black. The cut with achieves nothing. Black would be much better off to have played the marked stone as an extension down the left side. The marked stone is virtually a pass by Black, isn't it?