Issue resolved. Turns out that the Nikon camera mangles the FAT32 file system so that fsck_msdos dies upon trying to repair it (this is not a Pocket Edge issue, but a wholesale Linux issue. It seems fsck_msdos is in a very shoddy state).
Well, I found out that as long as I format my SD card in FAT16 instead of FAT32, PE can read it just fine. Limits the card size to 4GB which is about 800 pics on my camera, but that I can deal with.