Yeah the notification system on here is not the best...you get multiple notifications for the same notification. For example a friend request comes through as a notification and a friend request when it should only be a friend request. Similar thing happens when someone posts on your status...as a status on here is simply seen as a standard wall post, so when someone comments on it you get a notification because someone is commenting on said status but you also get a notification because that reply to your status is on your wall (in other words a standard wall post). This leads to major redundancy regarding notifications, i found myself with 8 notifications a few days ago but in reality there should of only been 4 or 5 notifications.
Simply put this is some bad programming.
Or a very very odd design decision