According to my knowledge of the forum rules, it is not permissible to publish referral links in the main topic or in any of the posts, whether they belong to the site owner or any of the publishers on the topic. However, it is allowed to add referral links to the signature space.
Not entirely correct, read this.
However, if you are using the forum as a publishing platform to host something really substantial and useful, selling ads in that substantial work is allowed. To be eligible for this, your post must be in a topic that you started, and your post must be substantial and long enough to make the ad seem entirely insignificant. If in doubt, ask me.
The proof is, if it's not allowed, these threads would be deleted from a long time ago.
1.
https://bitcointalk.org/index.php?topic=320959.02.
https://bitcointalk.org/index.php?topic=1458034.03.
https://bitcointalk.org/index.php?topic=5465749.0And many more.
The best thing you can do is to put the referral link in a signature design and mention this in your post for those who want to access the site to use the link in the signature.
You're talking about signature campaign where a campaign manager state to not edit your signature, but some of them allow you to use your own referral link. If you're not joining any campaign, you don't have to mention or saying anything, make sure you're not promoting NFSW/malware/scam or alike.