There's a rule to not add referral code or referral link as it's considered referral spam. I want to know that does that rule apply to everyone? Also, I want to know that is it okay to post referral code on some occasions or in some threads where there's possibility?

I've noticed that in various signature campaigns and some other threads where OP's sometimes post referral link of the platform that they're promoting with a message that if you've not joined the platform yet then you may join it by clicking this link, something similar.

I've noticed that, but personally I thought it might be fair use of referral link however in rule number 4 it's clearly stated that "No referral code (ref link) spam." that's why I want to know that something like that also fall into ref link spam or it doesn't?