Part of the couple of minutes apart issue could be due to the fact that some people are just slower at doing the actual post. So two people could be starting at around the same time and therefore, don't see each other's posts, but one of them takes longer to get it done.

When the mods instituted a minimum up-vote count for an anon to get one of those Pepe icons attached to their user name, I'm sure some people who really want one have been posting to that end. It's less than optimal to have to wade through volumes of duplicate info to check out interesting comments. At this point, they might as well keep producing duplicates because there's no way you can read everything on a daily basis like we used to even a year ago. With the influx of new people weighing-in with comments perhaps duplicates help with keeping the per-post comment count more manageable.