Just an interjection: a problem with using tags for semantical rather than visual representation is that the average HTML monkey at the keyboard will use these tags for their optical effect anyway. If he sees that <blockquote>s are displayed invented, he'll use <blockquote>s to indent things and the only way to prevent that would be to ask him about five times in a row whether he is indeed using the tag for a quote. The concept of semantical markup vs visual layout is a distinction that has to take place in the author's mind and cannot be made by his tool. Of course, the tool should make the distinction possible; but it can't enforce proper use of HTML. Sadly.
Makeshifts last the longest.