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If you did not know about this and you are actively buying, you need to reconsider whether you jumped in before you truly understood some very basic opsec practices.
That is all. You may now return to your pipes, needles, straws, tinfoil, and sugar cubes (yes, sugar cubes - I am THAT old)
Name one buyer in the entire history of DNMs, who was arrested via controlled delivery because their identity was determined through blockchain analysis.
I understand where you're coming from, but promoting this overly-paranoid attitude for random buyers is counterproductive, and has led to lost bitcoins, pointless 3% tumbling fees, and random nobodies assuming they're the FBI's next top target because they ordered a gram of MDMA.
If a buyer accepts a controlled delivery and charges are filed against them, ability to identify them through the blockchain will be simply irrelevant -- they're sunk regardless.