one function with a few lines addded to keep the structure of lisp forms when commenting a form inside another form

comment-or-uncomment-sexp.el

(defun comment-sexp--raw ()
  "Comment the sexp at point or ahead of point."
  (pcase (or (bounds-of-thing-at-point 'sexp)
             (save-excursion
               (skip-chars-forward "\r\n[:blank:]")
               (bounds-of-thing-at-point 'sexp)))
    (`(,l . ,r)
     (goto-char r)
     (skip-chars-forward "\r\n[:blank:]")
     (save-excursion
       ;; comment internal forms without breaking the structure
       (if (looking-at " *\)") ;;[:blank:] didn't work here(?)
           (progn
             (goto-char r)
             (newline-and-indent)))
       (comment-region l r))
     (skip-chars-forward "\r\n[:blank:]"))))

I added lines 11-15. The uncommenting part already works! yeah! ( As long as you are in the right position - you have to be "looking-at" a comment character)
This way the structure of the surrounding forms is still valid.
for example:

(let (x y)
;;  (not-sure) ;<- newline added after running `comment-or-uncomment-sexp`
) 

@Malabarba what do you think about incorporating these few lines?

Hey there. I'm having a look at this now.
Could you exemplify a case where the previous code didn't work?

What I mean is: comment-region is usually supposed to take care of inserting newlines and ensuring the code remains valid.