Often times, a player will have a clued card in their hand, but not know the exact identity of it yet. In these situations, the player might think that the team needs a playable card in someone else's hand, when the team really has it already.
For example, in a 3-player game:
Red 3 is played on the stacks. No blue cards are played on the stacks.
Alice has a blue 1 in her hand. She knows the exact identity of it, so it is known playable.
Alice also has a 4 clued in her hand. She does not know what color it is.
There are 0 clues, so if Alice plays the blue 1, Bob will be forced to discard.
Alice sees that Cathy has a red 4 on chop, which is playable. If Alice does not have red 4 in her hand, then Cathy could potentially discard the red 4 (after Bob is forced to discard).
Here, if Alice does not have a red 4, then doing a Generation Discard for Cathy's red 4 would be required. On the other hand, if Alice does have a red 4, then doing a Generation Discard for Cathy's red 4 would be redundant.
In order to cover both cases, Alice must take the more conservative approach and always perform a Generation Discard. These kinds of Generation Discards are called Cautious Generation Discards to differentiate them from the more ordinary kind.
After a Cautious Generation Discard happens, the next player is put into a tricky situation: was it really a Generation Discard (for Cathy)? Or could it be a Scream Discard (for Bob)? In order to cover both cases, the next player should not Chop Move, but they should also not discard on their turn.
For example, continuing the scenario from before:
Alice does not know whether or not the team needs Cathy's red 4, so Alice is forced to perform a Cautious Generation Discard.
Bob sees that Alice does indeed already have the red 4 clued in her hand. So, from his perspective, if Alice was performing a Generation Discard, it would be a Cautious Generation Discard.
However, it is also possible that Alice's move could be a Scream Discard for Bob.
Bob knows that in this situation, he needs to cover both cases.
Thus, Bob does not perform a Chop Move. Additionally, he does not need to clue the red 4 on Cathy's chop (because Alice already has it), but he will spend a clue in some other productive fashion. If Bob has nothing productive to do, he must "burn" a clue, similar to what happens when a Scream Discard occurs.
At the end of the game, it is normal for players to use a Positional Discard to get 1 card to blind-play, and to use a Positional Misplay to get 2 cards to blind-play.
If a player does a Positional Discard to only get 1 card when they could have performed a Positional Misplay instead, then this is quite strange. If they are not making a mistake, they must be trying to send an additional message.
In this situation, they intend for it to promise 3 blind-plays instead of 1.
For example, in a 4-player game:
The team has 0 strikes.
It is the End-Game and Alice sees all of the remaining useful cards. Thus, she can Positionally Discard or Positionally Misplay any card that she wants in her hand.
Alice sees that Bob, Cathy, and Donald all have playable cards on slot 2.
Alice blind-discards her slot 2 card as a Triple Positional Discard.
From Bob's perspective, he sees that Cathy and Donald have a playable card on slot 2. Thus, Bob expected Alice to perform a Positional Misplay on her slot 2 card.
When Bob sees that Alice performed a Positional Discard instead of a Positional Misplay, he knows that she must be intending for 3 blind-plays to happen (instead of 1) as a Triple Positional Discard.
Bob blind-plays his slot 2 card (to match Alice's slot 2 discard). It successfully plays.
Cathy and Donald are both in a similar situation to Bob. (They expected Alice to perform a Positional Misplay.)
Thus, they both know that this is a Triple Positional Discard, and blind-play their slot 2 cards (to match Alice's slot 2 discard).
In some specific situations, a Positional Discard from chop would not work, because it would just look like a normal discard. In these situations, a Positional Misplay would only get 1 blind-play (instead of 2) and a Shallow Discard would only get 2 blind-plays (instead of 3).
In a 5-player game, it possible to perform a Quadruple Positional Misplay, causing 4 people to blind-play from the same slot. (This works for the same reasons that a Triple Positional Discard works.)
For example, in a 5-player game:
The team has 0 strikes.
It is the End-Game and Alice sees all of the remaining useful cards. Thus, she can Positionally Discard or Positionally Misplay any card that she wants in her hand.
Alice sees that Bob, Cathy, Donald, and Emily all have playable cards on slot 2.
Alice blind-plays her slot 2 card as a Quadruple Positional Misplay.
From Bob's perspective, he sees that Cathy, Donald, and Emily have a playable card on slot 2. Thus, Bob expected Alice to perform a Triple Positional Discard on her slot 2 card.
When Bob sees that Alice performed a Positional Misplay instead of a Triple Positional Discard, he knows that she must be intending for 4 blind-plays to happen (instead of 2) as a Quadruple Positional Misplay.
Bob blind-plays his slot 2 card (to match Alice's slot 2 discard). It successfully plays.
Cathy, Donald, and Emily are all in a similar situation to Bob. (They expected Alice to perform a Triple Positional Discard.)
Thus, they all know that this is a Quadruple Positional Misplay, and blind-play their slot 2 cards (to match Alice's slot 2 discard).
When a Certain Finesse happens, players can blind-discard their Finesse Position card, because a Layered Finesse is impossible. However, when a normal Finesse happens, players cannot blind-discard anything, just in case a Layered Finesse is happening.
Sometimes, after a Finesse has occurred, but before the promised card has been blind-played, a teammate might find strategic value in duplicating the promised card.
If a teammate duplicates the promised card, and the duplication was not a last-resort, then it promises that the duplicated card is exactly on Finesse Position. This is called a Promise Clue.
The Promise Clue allows the recipient of the Finesse to blind-discard the card as a Promise Discard. (A Promise Discard is almost exactly like a Certain Discard.)
Finally, from the perspective of the player receiving the clue, if they play the duplicated card first, then they should know that the focus of the original clue was on the other, non-duplicated card, and they can go on to play it afterwards. (Otherwise, the original clue would be fairly low-value.)
For example, in a 5-player game:
It is the first turn and nothing is played on the stacks.
Alice clues red to Donald, touching a red 2 as a Play Clue. This is a Finesse on Cathy's red 1.
Bob sees that Alice has four 1's in her hand. This would be a juicy 4-for-1 clue.
Bob clues number 1 to Alice, touching four 1's: red 1, yellow 1, green 1, and blue 1.
Cathy knows that Alice performed a Finesse on her for the red 1. If she happens to play the red 1, then Alice will go on to misplay the red 1 as a purple 1.
Cathy also knows that it is possible that Alice performed a Layered Finesse on her. For example, Cathy could have purple 1 in her Finesse Position and red 1 in her Second Finesse Position. If this were the case, and Cathy blind-discarded the purple 1, then the team could lose the only visible copy of purple 1, which would be really bad.
However, because of the Promise Clue convention, Cathy knows that Bob has promised that the red 1 happens to be exactly on her Finesse Position and that no Layered Finesse is happening.
Cathy blind-discards her Finesse Position card as a Promise Discard.
Note that as long as the duplication clue touches two or more cards (e.g. with an efficiency of a 1-for-1), the Promise Discard interpretation takes priority over the Unknown Trash Discharge interpretation.