RE: Just a thought about comment-line

[Drew Adams]

> you comment the region with M-x comment-line.
> You will have the line at the point:
> 1.- not highlighted before M-x comment-line
> 2.- commented after M-x comment-line
>
> ...it doesn't happen on other "popular" editors.
> Could we consider a variable customise the behaviour
> and allow the last line not to be commented when the
> mark is at the start of line?

Yes, you can.  (And yes, Emacs should offer this
behavior out of the box, IMO.)

I use this command (I bind it to `C-x C-;).  It's
from library `misc-cmds.el'.

(defun comment-region-lines (beg end &optional arg)
  "Like `comment-region' (which see), but comment or uncomment whole lines."
  (interactive "*r\nP")
  (when (> beg end)
    (setq beg  (prog1 end (setq end  beg))))
  (let ((bol  (save-excursion
                (goto-char beg)
                (line-beginning-position)))
        (eol  (save-excursion
                (goto-char end)
                (if (bolp)
                    (point)
                  (line-end-position)))))
    (comment-region bol eol arg)))

https://www.emacswiki.org/emacs/download/misc-cmds.el