The "MyCryptoCode" is a random, unique identifier, we associate with the coins you send us. Since it's absolutely optional to use, for the best anonymity you can leave it blank. We do not associate the code with transactions you receive from us, so even if you were to use it, the trace is lost the moment your coins enter our mixer.
I was going to make mention of the same thing as @Khaled just did, I was actually saving it for my review.
Correct me if I'm wrong, I'm still not getting a total hang of this feature, so let's say I mixed a coin sent from Address A, and
MyCryptoCode is CodeA, and after a while I mixed another coin sent from Address B and using the MyCryptoCode A. will my CryptoCode A now ensure I don't receive coins from either address A and/or B when next I decide to mix ? Hence associating coins A and B together and so on.
for the best anonymity you can leave it blank.
I suggest you include this in the explanations, some would prefer to opt for the best anonymous measures