It's technically against the rules. The users posting referral links in the gambling section are the thread starter usually and posting a tracking link I think. I don't think those should be allowed either. Report them if you see them and see if moderators delete, then you'll know for sure.
Honestly thats what I believe either based on the rules on forum and read over some few threads here before regarding the referral code or link. That rule is set for a reason, but just like he said, he thought its allowed due to a lot of users doing it on gambling section.
But I believed worked with referral link are the one emdedded on signature code of a user.