well, if you think about it, putting tags on each individual track, including album, year, and every other good stuff would be more characters overall than a single comment field in one mp3.
like was said in the thread dealing w/ mk1 hdd limits, the ram is dynamically allocated, so i'm guessing that even tho the database has a 512 char array, it will only assign as much as necessary.
so i guess this becomes a wishlist for the next player release. up the comments field to 2048 =) that should be enough.