The point of the XKCD is not that the method is "secure" in an absolute sense. It is that it is a method for which the large group of people who would choose "

The point of the XKCD is not that the method is "secure" in an absolute sense. It is that it is a method for which the large group of people who would choose "Password0!" as their password [1] can use to create a password they can potentially remember, but such that the chosen password is "relatively" more secure than the basic alternative they would have otherwise chosen. [1] I.e. the far too common method of "pick a word, make one or two letters capitol, append a numeral, append a !".