Just ran into this bug after installing and uninstalling gdb64 (which depends on libc6-amd64).
Having root access does not solve the problem because rm and ln rely on libc6
~$ ldd /bin/rm
linux-vdso.so.1 => (0x00007fffd578e000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f37ad8ee000)
/lib64/ld-linux-x86-64.so.2 (0x00007f37adcd4000)
Time to dust off that installation DVD or make a new one if you have access to another machine.
I agree that this is an insidious bug for inexperienced users to diagnose because
the system becomes unusable and unbootable.
Dan