The word Spam which I bolded gave the rule number 4 a totally different meaning from what you might perceive it as.

If means when making post members are not allowed to spam the forum with referral codes or links but does mean you can't post a refer link when it's needed. You just don't spam it, link posting on every board with the link or code, for people to use it for your benefit like it is done in the good old days where refer is the most common task earn bitcoin or rewards.

---

For the perspective you are talking about if it's spammed then it's breaking the rule number 4