If you try to append to a file with no write permissions (say, the /etc/sudoers file which is is owned by root and has 0440 permissions), if you're the actual root user, this works. However, if you're another user using sudo, you get a permission denied error.
Why is this? It not because of the ownership of the file - it doesn't work with files owned by the normal user either. The real root user seems to have more permissions than are granted with sudo. What's the rationale for this? Is there a way to grant this permission to users using sudo?