Using darknet exchanges as mixers is unwise. There is not telling if the exchange is going to use the same BTC address to send you your coins back. That is the reason these exchanges are not targeted. Still running a non-KYC exchange on clearnet is a very bad idea. But I know of some, I wonder how and where are they hosted, so brazen!
Do you think darknet exchanges are created to help criminals? it means you didn't read the terms of exchanges. They're actually only help you to trade and protect your privacy, their services aren't to protect criminals. Remember, Bitcoin is using public blockchain and everything is recorded, it's not something you will able to fake it to erase your trace.
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