Add support for style tags in the TinyMCE editor. This can be done by adding the line
'valid_children' => "+body[style]", // Add style tag as a valid child of body.
after line 171 of the <moodledir>\lib\editor\tinymce\lib.php file

Currently the editor strips out perfectly valid style tags, causing experienced html writers to need to use standard web forms to edit text or to put styles within tags rather than using classes.