Dieter: Up to , Black lives. sure is a surprising move. It can be found when desperately looking for a way to make sente.
Tapir: Can't Black choose to start with (then , , and now ) to avoid ko? What is the status of the center white group after Black lives on the edge?
hhw: Seems to me that if Black starts with , , and . White will play the next move where is, and Black is caught.
Herman: No, in that case black will cut at and capture 5 white stones. But if black plays --- and then , white will answer at .
Bill: Yes, but the approach move is in the previous diagram. ;) If Black omits in this diagram, White can simply fill a Black liberty -- no ko.
Dieter: Huh? Black has to win the ko twice, White not.
Black should accept the ko. If here, he is short of liberties.