It seems that there is nothing in place to allow the text inside blocks like:
#+BEGIN_COMMENT ... #+END_COMMENT from having its face customized. It is possible to do this with quote and verse blocks, only not comment blocks. Would it be sensible to have a "default" block face which applies to *any* block of the form #+BEGIN_FOO ... #+END_FOO as long as it doesn't have a more specific face associated with it?
