span-ified bold/italic

I just noticed, the latest WordPress uses span with the bold/italics in styles instead of em and strong tags.

I think that’s a bad idea, because people with screen-readers lose out (but they don’t with strong/em).

But even if I’m wrong, I want WordPress to use strong/em. How do I turn this thingy off?! (I don’t mind recoding bits and pieces if I have to.)