Since <header> is intended to be useful to make subheaders not appear in the ToC, the move from<h1>Foo</h1> <h2>Bar</h2> to <header> <h1>Foo</h1> <h2>Bar</h2> </header>shouldn't, IMHO, result in ugly borders that everyone has to nuke (compare with <img border=0>).Yeah, that's a good point. I've left it at just display:block.
Four-and-a-bit years on I tend to agree :)