Comment 13 for bug 137136

The grub "quiet" option (or command if you like) - the one that is on its own line inside a menu entry stanza - only disables some messages that grub prints before the kernel boots. It does not alter the verbosity of the kernel nor of the start-up scripts. Unless there's a bug. See the Ubuntu grub source debian/patches/quiet.diff for more information.

Just for comparison: the kernel "quiet" option (or parameter) - the one that is on the kernel line - tells the kernel to be less verbose, and is also probed for by the start-up scripts (see /usr/share/initramfs-tools/init and /usr/share/initramfs-tools/scripts/init-top/usplash and /etc/init.d/rc). This bug report is not about this one.