Luckily, a feature of Bloglines comes in: Bloglines, as all feed readers, is originally meant to read feeds containing links from a source where every link points to the source site itself, not to external resources, like the del.icio.us links do. So it interprets multiple entries with the same link (= differently tagged submissions of the same link by multiple del.icio.us users) as updates of the same entry, thus keeping the list unique.

So in order to make the greasemonkey tag feed on del.icio.us contain unique URL’s, submit it to your Bloglines account to browse through: have a look at this preview of the greasemonkey links.