Here's something she doesn't mention in the post: to include your copyright information in your query letter or on the manuscript itself looks amateurish. If you wrote it, of course it legally belongs to you; that's what copyright means. Amateurish, and maybe a little bit paranoid too; I admit it's a bit of a red flag for me, in a query letter, that the writer may prove difficult to work with. Good relationships are built on trust, and that's a poor way to begin.
(That whole thing about mailing the work to yourself and putting it in the freezer is a myth, too, of course.)
Can you think of any other publishing- and writing-related urban legends?