Q. Can your method protect against my noxious brother/cousin/guest users?
A. Probably not by itself; the main purpose of locking the kernel is to foil remote exploits (malicious software that is installed automatically and surreptitiously when you visit a hostile/compromised Web site, and sometimes simply when you have an active Internet connection). An even safer practice is to employ my method in a limited account. If this is too restrictive for you, then setup such an account for other users, and password-protect your own account as well as the Administrator. This way, they will be protected from remote attackers as well as themselves.