Comment by high_na_euv

>2) spends funds at an ecommerce site (dirty funds) 3) secure a paypal refund WHICH GOES TO ANOTHER ACCOUNT (clean funds)

How it breaks the chain?

Account1 buys for 10k USD, requests refund, receives it?

Even if it went for some reason to account2 then there is still the chain, but why would it go to other?