While reading the Emacs manual in Emacs using Info-mode, I found that
non-ascii characters are displayed as octal escape sequences rather than
rendered as glyphs. To repro:

- start emacs with -Q
- open the emacs manual and start a search: C-h r s
- search for a section with non-ascii chars: it requotes text typed<return>
- the found sentence reads:
> For example, it requotes text typed `like this' to text \342\200\230like
this\342\200\231.
- if correctly rendered, it would read:
> For example, it requotes text typed `like this' to text ‘like this’.

If I select the text and write the region to a file, I can open that file
and Emacs renders it correctly. I tried to remedy this by adding the
following to my init file (and commenting out the rest of the file):

(prefer-coding-system 'utf-8)
(set-default-coding-systems 'utf-8)
(set-terminal-coding-system 'utf-8)
(set-keyboard-coding-system 'utf-8)
(setq default-buffer-file-coding-system 'utf-8)

The only effect this had was to change the default coding system for new
files from utf-8-unix to utf-8. Running `describe-coding` in the Info
buffer reported
> Coding system for saving this buffer: t -- raw-text-unix
both before and after adding the above settings.

I also tried both gui and terminal, with and without the above settings,
and saw the octal escape sequences in all cases.

My Emacs version and configuration:

In GNU Emacs 25.1.1 (x86_64-apple-darwin15.6.0, Carbon Version 157 AppKit
1404.47)
 of 2016-09-21 built on MachineCode.local
Windowing system distributor 'Apple Inc.', version 10.11.6
Configured using:
 'configure --enable-locallisppath=/usr/local/share/emacs/site-lisp
 --infodir=/usr/local/Cellar/emacs-mac/emacs-25.1-z-mac-6.0/share/info/emacs
 --prefix=/usr/local/Cellar/emacs-mac/emacs-25.1-z-mac-6.0 --with-mac
 --enable-mac-app=/usr/local/Cellar/emacs-mac/emacs-25.1-z-mac-6.0'

Configured features:
NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Info

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mac-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
  buffer-read-only: 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. [2 times]

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode cl-loaddefs pcase
cl-lib mail-prsvr mail-utils jka-compr info easymenu mule-util time-date
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel mac-win term/common-win 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 kqueue mac multi-tty
make-network-process emacs)

Memory information:
((conses 16 113689 6270)
 (symbols 48 20181 0)
 (miscs 40 73 185)
 (strings 32 19396 4598)
 (string-bytes 1 510009)
 (vectors 16 12204)
 (vector-slots 8 426977 6597)
 (floats 8 169 118)
 (intervals 56 4622 16)
 (buffers 976 19))