I totally didn't know that was a feature. Don't know if I can still call myself a Pokémon fan. ;)
Oh man, really?! Mine will be filthy then 'cause I didn't even know!You can also clean your badges in Black and White too. Although, after playing Diamond and Platinum for so long the novelty of it sort of wore off by the time they were released. So I never really bothered to clean my badges as much in White as I did at first in DPPt.