Tapir found this somewhere on SL (this was without comment on the status). But what is the status of the corner?
fractic: Isn't this a case of two hanes gain a liberty and black can kill without ko? Black has actually got 4 liberties in the diagram to the left.
tapir: I don't know the semeai heuristics very well, but it surely looks different to me.
unkx80: How about this?
fractic: This does favour Black though. Black takes first and White has an aproach move at a. Of course could also cut but in that case Black has ko threats by extending from .
symplicity: seems risky. Black can extend from for threats, but this can lose a lot of points if white wins the ko. White can make it 2-step approach ko if he jumps ahead after pushing once, and all of black's threats will have become greatly loss-making.
I think might be better for black in a lot of cases. It's still a 2-step approach ko, but black will suffer no damage on the left.
Same thing this way.
I don't know if there's a way for black to kill unconditionally in the first place, though.
Tapir: The professional practice to play this repeatedly after 4-5 4-3 keima tenuki... indicates that it is not too one-sided. A clear result in the corner would be one-sided to my eyes. However, the SL page just presented the result without indicating the status. I feel giving a joseki without understanding the resulting position isn't good. Maybe Black at b (first diagram) is a way to compromise, if Black can't gain from a ko.