Well, is it allowed or not?
Just to clarify, I am not affiliated with the site. I promote referral links to the site. I want to promote my referral links in a signature campaign. It's for a particularly lucrative referral system.
I just want to make sure this is allowed....
Yes, it is allowed to be placed in the signature. However, do take note that signatures may not offer a very high hit rate, and the rates for signatures are very competitive out there. Perhaps you can create a thread to offer rewards to those who signup under you and remain active.

Noted. Thanks for your reply. Yeah I would give it a trial run of 1-2 weeks and then decide whether to continue based on the results. I expect a low hit rate generally, I just need to see if I can optimize it enough by targeting certain sections (Speculation, Trading Discussion, etc).