If I understood you correctly.
If you used "nofollow" in your referral link and site your referring to has a username with "nofollow" then he/she will get the direct referral through your link/banner.
But if you want NOT to have direct referrals then just write site name [which I see pointless].
Anyway, hope this answers your question.
No, I WANT to have direct referrals. I have a blog for my ptc sites, so my question is - Can I make ref links nofollow so that my blog is more SEO friendly?