spacedog

What I say is 100% correct for DEFAULT CAMPAIGNS.

Login to your account. Click link codes.

find "Switch between Encoded or Decoded link codes" click [Switch]

You will miraculously see the unencrypted link code and that it indeed does include your username in the code.

Now, if you have a campaign set up, like for adwords, you will see this also in the unencoded link, usually represented as a series of numbers.. so, decoded would be like this:
username;123456:param:param.

Now, since there is a campaign, you end up with an entirely different NATS code because that's what base64 does.

Trust me, you're not being fucked here.