I understand what you are saying, but here's an example. Yesterday I was on the Sitepoint forum, and there was a question about getting adwords coupons. I remembered your article on the subject and posted a link to it. But Sitepoint is also nofollow so you aren't getting any benefit from it. How can that be right?
I appreciate what you say about UGC but that's what moderators are for isn't it? Sitepoint could delete my link if they thought it inappropriate, but instead a genuinely placed link will go unrewarded (in the terms I am talking of).
In addition, this isn't limited to UGC sites.