Nobody ends up with a "the other coin", it ends up as a transaction with many inputs and many outputs on the chain, but none are 1:1 mapped. The sum of inputs a

Nobody ends up with a "the other coin", it ends up as a transaction with many inputs and many outputs on the chain, but none are 1:1 mapped. The sum of inputs and outputs just has to match. So given sufficient inputs and iterations, and keeping in mind that you can split up outputs into as many wallets as you want, it becomes hard to differentiate. You can of course treat it all as tained, but you'll have a lot of small fish and privacy users in the middle to track down as well.