This is a followup of MDL-29768

From Sam Hemelryk:

Two things I think would be good improvements (albeit I don't know if everyone would agree).

• If $component is empty display `moodle` (for consistency)
• Wrap the {foo/bar}

  in a tag with a CSS class - perhaps <em> so that a) it is easy to visibly identify without styles and b) themer's can do whatever with it.