Move I've played for a few years without understanding it.

[Harleqin]

'd' looks dubious to me

Aji. No need to use it with bad timing.

If I was in a sarcastic mood, I'd say that the "aji" of my opponent playing a bad move leaves me rather unworried.

Ah, darn, now I have said it anyway. Nevertheless, I simply do not see the value of the potential of butting a group into an existing hane, especially when White does not even really have the time to play the prerequisite move. What kind of timing do you have in mind? Do you see a way to make this a double threat? Is that really bigger than protecting the cut on the lower side?

[RobertJasiek]

1) White extends upwards for eyespace.

2) Later, when surrounded from above and left, White increases his eyespace by a move like d.

3) Yet later, White attacks the aji.

[mitsun]

$$W Local tesuji.
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . O . . |
$$ . . . . . . , . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . O O . . |
$$ . . . . X . X . . . |
$$ . . . O X . . X . . |
$$ , . X X O O X . W . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$---------------------

Click Here To Show Diagram Code

[go]$$W Local tesuji.
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . O . . |
$$ . . . . . . , . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . O O . . |
$$ . . . . X . X . . . |
$$ . . . O X . . X . . |
$$ , . X X O O X . W . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$ . . . . . . . . . . |
$$---------------------[/go]

The position still looks good for B, but W does have a tesuji to gouge out some of the corner (or revive two dead stones).