When you post a FPP to the Blue, your links are automatically run through some sort of search function to see if they have been posted before. This might be, if not too site-intensive, a useful thing for comments as well, so that people don't find themselves posting the same links, with different flavor text.
Currently, as it stands, there is no such mechanism, and since people rarely post links under the specific link itself, but rather a flavor text referent, the same links are often posted multiple times, particularly in long threads or series of long threads. I don't want to link to any examples, because I don't think it's anything anyone should be embarrassed about - there's no good system for fixing it currently - but it is something that does come up, meaning the same link is posted again and again, unknowing.
This could also be useful as someone wanting to post a link in the comments would be able to see where the link has been posted before, and reference some of the commentary that arose in response to said link. I'm not sure how others feel about it, but I think it would be a net positive to the site.