There are a variety of ways but obfuscation of affiliate links is very complicated. You want something like a double meta refresh- which has been talked about plenty in other posts. This will blank the referrer (so they just see (none) as the referrer.) If you're worried about spam complaints then you have to do a lot more than the simple methods to hide your shizz and nothing is 100% if they do enough digging for w/e method you use they'll find you out.