[frostschutz]

So what happens after unplugging the Kobo from USB?

Nickel spawns two processes, one is `dd if=/dev/mmcblk0p3 bs=512 count=1` (read the first sector of the data partition, not sure why nickel needs dd for that but okay), then it does something with that data and spawns `dd of=/dev/mmcblk0p3 bs=512 count=1` so the first sector is overwritten. (perhaps it's forcibly resetting the factory reset counter to 0?)

Replugging the Kobo to USB and Windows no longer mounts and fsck.fat complains about differing original/backup sectors again.

I think Kobo definitely needs to stop messing with this sector. There happens to be a free sector right next to it (last sector of the recovery partition is unused because that happens to have an odd number of sectors)... or just use a file in the rootfs already, what's the point of messing with these sectors in the first place.

Still unclear how this behaves any different when Windows formats it.

Maybe I should try copying original to backup instead and hope that the first sector is always messed with in a way that stays identical to the backup.