Originally Posted by PBucksJohn

Are you talking about the referral code for sending to the affiliate program itself?

That can be linked two ways. It can be linked directly with the /?user=13 like you said or it can be setup as a full site in NATS and linked with the normal link codes and tracked via campaigns, etc. That is why you might see it both ways sometimes. The vast majority of programs use the 2nd method and set it up as a full blown site.