Let foo.txt have this text:

xxxxx xx x xxxxxxx xxxx xxxx xxxxxx xxx xxxxxxx xxxxxxxxxx. xxxxx xx x
xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xx x xxxxxxx xx
xxxxxxxxxxxxxx. xxxx xxxxxxxxxx xxxxx x xxxxxxxx xxxxxx xxx xxxx xxx'x
xxx xxx xxxx xxxxx xxxxxxxx xxxxx.

Select all of the text and execute the fill-paragraph command.

Expected:

xxxxx xx x xxxxxxx xxxx xxxx xxxxxx xxx xxxxxxx xxxxxxxxxx. xxxxx xx x
xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xx x xxxxxxx xx xxxxxxxxxxxxxx.
xxxx xxxxxxxxxx xxxxx x xxxxxxxx xxxxxx xxx xxxx xxx'x xxx xxx xxxx
xxxxx xxxxxxxx xxxxx.

But it leaves it unchanged. It seems to let the space following the
period unduly influence whether to pull the word up to the second
line.

---

In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.10.4)
 of 2013-06-18 on psd15
Windowing system distributor `The X.Org Foundation', version 11.0.70101000
System Description:    Red Hat Enterprise Linux Client release 5.4 (Tikanga)

Configured using:
 `configure
 --prefix=/redacted/user/boreilly/sw/emacs-install-trunk-20899d085afe62520113b5acbfe3dbba57823dc9
 --with-gif=no'

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Text

Minor modes in effect:
  tooltip-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 input:
<help-echo> <help-echo> <help-echo> <help-echo> <down-mouse-1>
<mouse-movement> <mouse-movement> <drag-mouse-1> M-q
<down-mouse-1> <mouse-1> M-x r e p o r t <tab> <re
turn>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
foo.txt has auto save data; consider M-x recover-this-file

Load-path shadows:
None found.

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