In a twist of my adventures, I apply the data=writeback,nobh option to fstab but not to menu.lst as well. Rebooted - and got a read-only / with a failure to load. Couldn't edit fstab either, because it was read-only as well. Not a good situation to be in when I wasn't quite sure what the eCryptfs passphase was.
Managed to remount it with "mount --no-mtab -o remount,rw /dev/sda1 /" and edited the file back, though!