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i'd be be curious to know how much volume he was running through his account, given their response about sourcing bought coins via coinjoin and the fact that nopara73 was able to deposit/withdraw using outputs from the flagged addresses.
Because the guy didn't say everything perhaps, we don't know what he was doing with his account. Look for example the other guy who commented to say they locked him because he used the darknet... It could be the same for the first guy.
I doubt the problem was really Coinjoin, since someone else tested the address too.