...so then trace the transfer to each identity? How does knowing the first person in the chain help identify the 2nd and 3rd, etc? What if there are 50 identities and the coin has a dozen origins?
That's the part about the user being careful how they got their money into the system.
You're also assuming Ethereum-clone chains work the same way as Bitcoin. They do not. An Ethereum wallet has a single long-term identity.