Glen, if you're going to spend some time on newcomment please have a
look at the below.  I once asked Stefan but apparently he forgot.

With emacs -Q customize `comment-style' to box or box-multi.  In
*scratch* insert

(foo bar baz)

set the region around bar and do `comment-region'.  Gets you

(foo ;; bar ;; baz)

instead of

(foo ;; bar ;;
      baz)

Responsible is the

     (when block (unless ce (setq ce (comment-string-reverse cs))))

line in `comment-region-internal' which makes the subsequent

       (unless (or ce (eolp)) (insert "\n") (indent-according-to-mode))

fail.  I proposed the attached patch.