In PRE elements, newlines that appear inside inline elements (CODE/STRONG/etc.) are converted to spaces in the editor. The loss occurs when the content is being pulled from the TEXTAREA.
The Fiddle has a pretty clear demonstration.
http://core.trac.wordpress.org/ticket/19666
I started to see this behavior some months ago after a WordPress upgrade. It's possible that WP was formerly converting all newlines to BRs before passing the content to TinyMCE, but it seems like a TinyMCE bug nonetheless.
If you wish to follow or post a comment, you need to be registered and logged in.
Comments
mrclay
Fixing tinyMCE is beyond me, but I did find a workaround: add a onBeforeSetContent handler that converts newlines to BR inside PREs.
Workaround in action: http://fiddle.tinymce.com/89aaab
mrclay
Sorry, the workaround is at: http://fiddle.tinymce.com/cAaaab