It would be handy if there were some way to remove unsuccessful ping attempts from the unsuccessful ping list. It seems a distinct possibility that one would not want to have the option to retry the manual ping (say, it had a typo), and therefore would not want it to appear on that list anymore.

This sort of thing would probably only be needed for manual attempts. Then again, since the module does not track whether an URL was automatically harvested or manually entered, perhaps it would be easier to allow removal for all unsuccessful pings on the list.