But in this case, I really want to know if someone who 100% posts a referral link on this forum as a real effort to increase the traffic of his site or personal blog is not breaking the rules? I may have forgotten something.
Spamming of referral links around the forum would definitely be breaking No. 4 of the unofficial rules.
That may not apply here as the user is not sharing referral links, but rather backlinks to their website (I assume both the profile and the website are affiliated, judging from the name).
This still borders on spamming in my opinion as the user is recklessly creating threads to try and increase the traffic to their website.