parameters (like \UNIX) are commonly entered using an empty group to
separate the markup from a following inter-word space; this is not
needed when the next character is punctuation, or the markup is the
last thing in the enclosing group. These cases were marked
inconsistently; the empty group is now *only* used when needed.
letter and end with proper punctuation. "Documenting Python" will be
updated accordingly so that this will be editorial policy for the Python
documentation.