> That is, more or less, the reason why W3C recommends using <em> rather than <i>. Ideally the ''double apostrophe'' in wiki-syntax will insert <em> (now it inserts <i>)

I absolutely agree with your point. I wasn't aware that wiki-syntax inserts in fact <i> tags (and also <b> tags, which bring up the same problems). That needs to be changed. We need clean, semantic markup in order to adjust the styling to any given circumstances, as you perfectly described.

Speaking of semantic markup, what do you guys think about replacing the standard 'bold' and 'italic' buttons in the visual editor with a simple 'emphasis' button? In my opinion, that would help a lot with these kinds of problems. In my opinion, we should make authors think less about presentation (that's our job) and more about content.

best, max.
@awesomephant