Strange display behavior after filling

[YAMAMOTO Mitsuharu]

I found some strange display behavior after filling.  In the
following, "row" means a displayed horizontal segment, and "line"
means a sequence of characters delimited by newlines.

  1. emacs -D -Q
  2. M-q  (I'm not sure why this is needed.)
  3. Insert "123456789 " (without quotations or newlines) 18 times.
     Say, C-x ( 1 2 3 4 5 6 7 8 9 SPC C-x ) C-u 1 7 C-x e.
     It is displayed in three rows.
  4. M-<
  5. C-u 1 C-v

Now the first row becomes continued to both directions.

  6. M-q

Then the first row is displayed shorter than the second one, whereas
they have the same number of characters.

  7. C-p C-n C-n

The line number in the mode line says the cursor is at the third line.
But it is displayed at the second row that corresponds to the second
line.

                                     YAMAMOTO Mitsuharu
                                address@hidden


In GNU Emacs 22.0.50.1 (sparc-sun-solaris2.8, X toolkit, Xaw3d scroll bars)
 of 2006-04-11 on church
X server distributor `The XFree86 Project, Inc', version 11.0.40300000
configured using `configure '--x-libraries=/usr/local/lib' 'CFLAGS=-g -O2 -mv8 
-DSYNC_INPUT''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ja
  locale-coding-system: japanese-iso-8bit
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  auto-compression-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t