Somebody just shared this on Reddit, and it’s quite interesting, so I’m sharing it here.
Apparently, in this situation, the 3 white stones on the bottom right are considered alive under Chinese rules. If black takes them, white can start the ko on the top right and black can’t fight the ko.
I created a demo board with the variations here.
I wonder how this situation is handled in Japanese rules.
Maybe we need @yebellz input for the Japanese rules 
can you show the variation? I’m not seeing how the bottom right becomes a ko threat
What if black don’t take the 3 stones? How is the scoring? Seki for both groups?
Second point: black could maybe keep a ko threat before in the game so that he can resolve the situation.
Yes it’s seki because neither White nor Black have ko threats.
Seki for both and in that case it seems like white wins.
Well if white succeed to put a trick like this I won’t be ashamed to lose.
Ah my bad i didnt see the demo board. That’s a wild threat!
I think the idea is that black can claim the three white stones are because when you play the ko in the L&D resolution only passes lift ko bans. So white wouldn’t be able to recapture the ko after making a normal ko threat.
I think it would make the top right would be seki for the same reason as neither player could capture the other by starting the ko in this special dispute rules.
Sorry, I don’t understand what you are saying here. Are you talking about black taking the 3 stones or not taking? If black takes then there’s ko, but if black doesn’t take then there’s no ko.
In Japanese rules, both players pass and black claims the three white stones are dead. White asks black to prove it. Black takes. White starts the ko. Black takes in the corner. White passes as that is the only valid ko threat in the hypothetical play phase. Black takes again. White passes. Black wins the ko. The white stones are proved dead.
That’s my understanding anyway. Might be wrong.
Why wouldn’t White play N2 instead, like in Sadaharu’s variation?
Yeah, you’re right, I’m making no sense!
Wait, I expected this reply:
Well I guess yebellz will be along to sort it out. But now I’m wondering if there’s something about life and death being considered locally only in Japanese rules so that the pass as ko threat thing makes sense?
Yeah I’m talking about Japanese rules
It’s just a different ko rule. Only passing lifts the ko ban, at least as far as I’ve come across.
You can answer any ko threats that aren’t a pass and the opponent can’t recapture the ko.
It’s very confusing and I’m easily confused anyway!
Very neat position!
As you’ve already demonstrated above, it is a seki under Chinese (and other area scoring) rules, as Black attempting to capture any White stones would backfire with one of the Black groups dying.
The game is in a terminal position (i.e., no strategically worthwhile moves left to play and both players should pass), and I believe the correct ruling should be a seki in the top-right, and White’s three stones are dead in the bottom-right.
As worked out by @teapoweredrobot and @shinuito above, the key difference about Japanese rules is that determining life and death during scoring involves considering hypothetical play outs, while applying a different ko rule, which I wrote about in this post:
By the way, for people that like this sort of thing, I wrote about another case here:
