@baris thanks. I realised there's some issues with redactor munging the data.
When code is insered inside a <pre/> block, switching between HTML and WYSIWYG views will munge the content to HTML entitites.
You can recreate this issue on this page:
Switch to code view and add some HTML inside the <pre/> block. I entered:
Switch to WYSIWYG and back to code and it has been replaced by:
This breaks the ability to parse that code later with syntax highlighters.
I've raised it with Imperavi.