Yeah you will have more answers on the Hanabi subforum.
I wrote that guide
Short answer: Double half bluff have priority.
Long answer:
The bluff (like explained on bluff seat) consist on making the next player answer immediately because if he is allowed to wait, that can be really fast really hard for everyone to follow everything (and make some extra moves not possible anymore).
So:
B: b1-x-x-x
C: x-x-x-x
D: x-r2-x-x
A clues red to D: B assumes r1 and must answer.
Once b1 is played r2 is known.
Now take that situation:
B: b1-x-x-x
C: ?-?-?-?
D: x-r2-x-x
A clues red to D. B discard. Now it's your turn as C. Without layered finesse you are supposed to have exactly r1. If you got y1, then B isn't allowed to discard.
Now let's said you play your first slot and it's not r1 but y1. Then B is still not allowed to discard... Unless you got r1 in slot 2. That's a layered finesse.
Now take that extreme situation:
B: (5)-(5)-(5)-(5) all those 5 are known
C: ?-?-?-?
D: x-r2-x-x
A clues red on r2 to D. B does something unrelated (green clue on g1 to A). Now as C you play your first slot and it's y1. What should you do now?
Here we got a big problem because B couldn't answer that clue. Do you assume B 'should answer' and so it's layered and you got y1+r1?
Or do you assume since B knew what was going on, it's still a bluff, and nothing else can be deduced?
Really try to undestand why it's a problem here.
Now to finally answer your question:
B: r1-x-x-x
C: y1-x-x-x
D: x-r3-x-x
A clues red to D. B saw nothing to connect. He can have r1+r2. He is in bluff seat, so that could be a bluff. Maybe he have b1. But then r3 would not connect. So maybe B have b1-r2-r2-x. But then from B's pov, it's still undefined what he should do after. Does he has instead b1-r1-r2-g5? But anyway B should play because half bluff are pretty commun, and it's way more likely that him having 2 or 3 cards (with half bluff he only has r1). So he plays r1.
Then C assumes he has r2. On theory, he isn't on bluff seat so that should be a layered finesse. But like I said just before, B was forced to play r1. So since B was forced, C is in bluff seat too. And so after he played y1, r3 is known.
To finish, take A's pov on the previous situation:
B: r1-y4-g3-g4
C: y1-g5-b2-r4
D: g2-r3-b5-y4
You could for simplicity decide to not play with double half bluff. But that mean on that case, what should you do as A? If you clue something like blue to C, then B will be forced to answer since B could have y1 in slot 1. It's pretty sad to not be able to get r1+y1+r3 while that make sense with everythin said previously.
Double half bluff was added before layered finesse in both bga and hgroup, because that work well even without layered finesse which have a trickier logic. So after adding layered finesse (which is extremely more powerful than double half bluff), removing a 'logical' move look sad.
So that's why Double half bluff exist
If you want to answer please pm me or create a subject here:
https://boardgamearena.com/forum/viewforum.php?f=102 .
