init_myformat(): None of the "mark" values can be empty strings, or

init_myformat():  None of the "mark" values can be empty strings, or
    LaTeX2HTML feels free to remove a surrounding element that
    contains no other content.  Since such an element is typically a
    named anchor used for hyperlinking, they should not be removed.
    Unfortunatley, making sure these marks are non-empty is the most
    direct way of avoiding this behavior.

Thanks to Dave Kuhlman for tracking this down; this was some excellent
detective work!