Subject: bug#21921: New function comment-line also comments first line after region

From: Clément Pit--Claudel <[email-masked]>
Date: Sat, 14 Nov 2015 13:24:23 -0500

Hi all,

The new comment-line feature is very convenient, but I find its operation slightly confusing wrt the "comment out region" feature.

Its documentation says:

  If region is active, comment lines in active region instead.

However, it seems that it also comments out the line just after the end
of the region.

For example, given the following text

abc
def
ghi

Placing the cursor before `a', then pressing C-SPC C-n C-n, causes two
lines to be marked: (> is highlighting, | is point)

>abc
>def
|ghi

Yet pressing C-x C-; (comment-region) comments out all three lines.

Similarly, again starting from 

abc
def
ghi

placing the point before `g' and pressing C-SPC C-p C-p causes two lines
to be marked:

>|abc
>def
ghi

Yet pressing C-x C-; comments out all three lines. I find this second example especially confusing.

Is this behaviour only surprising to me?

Cheers,
Clément.

In GNU Emacs 25.1.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8)
 of 2015-11-14
Repository revision: 02bf89f857e04b8023ce03eadcfa87c82918e957
Windowing system distributor 'The X.Org Foundation', version 11.0.11501000
System Description:	Linux Mint 17.2 Rafaela

Configured using:
 'configure --with-x-toolkit=gtk3'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LC_TIME: en_DK.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message dired format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns help-mode easymenu cl-loaddefs pcase cl-lib mail-prsvr
mail-utils time-date mule-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 80441 7581)
 (symbols 48 19255 0)
 (miscs 40 38 110)
 (strings 32 12779 4612)
 (string-bytes 1 365820)
 (vectors 16 10757)
 (vector-slots 8 419611 2876)
 (floats 8 143 70)
 (intervals 56 194 0)
 (buffers 976 11)
 (heap 1024 25940 1037))