In reply to Keith Davis.

It doesn't strip out standard HTML like Strong or Emphasis but if you use embed code for an iFrame, that type of code will be jumbled together. Thanks to oEmbed support though, you don't have to use that embed code. Just placing the URL to the video on Youtube on it's own line will automatically embed the video on the post when it's published.

Are you constantly publishing flash or weird non HTML standard code or something?