So the Jokers get placed in your hold after you're cursed. This is just to keep track of them for the feats at the end of the game I assume, it wouldn't count as a Knowstone correct?

Yep. for Feats (so now you check everything in one place) and because you need to track how many Knowstones have been stacked on it to lift a Curse (once you have Calm Mind ability).