I just tested out bitmixer. My new coins have 100% taint to the thiefs original address. Should I be worried about using them on exchanges with my real name?
This is an expected result. For a while now all the BTC coming out of bitmixer will be "tainted" by the stolen coins. That is, if you believe "taint" means anything at all. That is like saying this $100 bill in your pocket was used by several people in the past and one of those people used it to buy some drugs. Is the $100 you have in your pocket "tainted" by the crime several owners ago? No. It is just a $100 bill - it is fungible.
However, as a point of fact, the BTC you received from bitmixer are
not "the stolen coins" or even "parts of the stolen coins". They are UTXOs that happen to be traceable in whole or in part though various transactions back to the original UTXOs that were taken from klee. So this question of "stolen coins" and "taint" is not as clear cut as some in this thread want it to be.
Assuming BTC are fungible then you have nothing to worry about.
A previous post likened the entire operation of the bitmixer to this: a thief gives someone $1,000,000 in cash and this person turns around and gives the thief a different $1,000,000 in cash, maybe in different denominations, maybe minus a fee.
Now in this transaction did the thief "wash" his ill gotten gains? NO. He still has $1,000,000 (minus the fee) in ill gotten gains.
Did the person that "made change" for him do anything wrong. NO. They started with $1,000,000 in cash that they got from working hard, selling products and services, etc. and ended up with $1,000,000 plus maybe some sort of fee. Why did he charge a fee? Because it takes a long time to count $1,000,000 in cash given that the largest bill in circulation is only $100. But I digress.
The point is that changing out one bunch of cash for another bunch of cash does not in anyway "launder" the money. To launder money the thief has to be able to show that the money came from a legit source, enterprise, business, etc. Also, making change does not in any way hide the crime. In this case the thief started with $1,000,000 in ill gotten gains and ended up with $1,000,000 minus the fee in ill gotten gains - money laundering has not taken place. Upon finding the thief with their money the authorities would have their man and the stolen money. The fact the cash is not the same cash he took is not material. The only thing that might be considered for claw back might be the fee. However, if the thief bought a hamburger with some of the money would they go try to get it back from McDonalds?