I realize I'm a bit late to this particular party but I didn't want to duplicate a feature request about deduplication. I have seen a couple other similar requests (like this one), so this seems like a feature folks would like to have. And I'm not sure that the "Context" feature really does the trick, as it's only engaged after you've already perhaps clipped a duplicate page. Optimally, engaging the Clipper on a page would compare the URL to our notebook(s) and if a match is found would alert us that we've already clipped that page, leaving the user to decide what to do with that information. Cheerio!