We know they're prepared to transmit child porn to pedos, and run a market over which other people sell drugs to each other. But if they controlled a vendor's account (like iCoke on Dream), could they receive orders and ship the drugs? Would that even be legal or stand up in court? Assuming no controlled delivery for immediate arrest on arrival.
If not, then assuming the market itself is not compromised and LEA haven't swapped out vendor PGP for MITM, every vendor that anybody has sucessfully received an order from (ordered since the Hansa takedown) is safe. If they were LEA, nobody would actually receive a package from them.
Sorry if this is obvious to everyone else. It allows us to potentially build a 'whitelist' as well as the compromised vendor 'blacklist'.
I remember watching a documentery that said that police can do anything but introduce new drugs into the system. Which is why a lot of people force whoever they're talking to to give them a joint before doing business to see if they're a cop or not.