This means that the referring website your link was posted on was tagged as spam.
It seems that people are only finding out that their accounts are banned if their referral says they are, does the owner of the account have any way to tell if their account has been banned? ie an email or being unable to sign in. I just want to make sure my referral link is not being misused in any way.
You are not banned as a referrer, but if the source of the referral on an individual basis is spam, it won't count toward your account.
But on the front page it says "spam referral methods will result in account termination without notice" doesn't that mean that if you just go spamming you referral link all over the place eventually your account will be banned?
Yes.