People are trying to address the wrong issue. CCP could easily fix the spam just by making a verbal rule prohibiting it. The people spamming are dedicated players who obviously don’t want to get punished, so they’d stop if it became forbidden. Only a small amount of spammers would continue to operate, composed mostly of those who don’t know the rules and a handful of disposables farming injectors and/or marketable rewards specifically, both of which could be easily policed.
Or, hear me out, just stop providing any benefit to the person who is handing out the link. The spam will stop immediately. New folks can still be referred, it just won’t give the person providing the referral any benefit outside of helping out a new player in their corp.