Here is the man page source code of /usr/share/man/man1/docker-attach.1.gz:
#+BEGIN_EXAMPLE
  .PP
  To override the sequence for an individual container, use the
  \fB\fC\-\-detach\-keys="<sequence>"\fR flag with the \fB\fCdocker
attach\fR command. The format of
  the \fB\fC<sequence>\fR is either a letter [a\-Z], or the \fB\fCctrl\-\fR
combined with any of
  the following:
  .IP \(bu 2
  \fB\fCa\-z\fR (a single lowercase alpha character )
  .IP \(bu 2
  \fB\fC@\fR (ampersand)
  .IP \(bu 2
  \fB\fC[\fR (left bracket)
  .IP \(bu 2
  \fB\fC\\\\\fR (two backward slashes)
  .IP \(bu 2
  \fB\fC\_\fR (underscore)
  .IP \(bu 2
  \fB\fC^\fR (caret)
#+END_EXAMPLE

I live in timezone UTC+8. Sorry for the delay and thank you for your
patience.

On Wed, Jul 13, 2016 at 1:50 AM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Meiyo Peng <meiyo.peng@gmail.com>
> > Date: Tue, 12 Jul 2016 16:12:41 +0800
> >
> > The underscore character "_" is displayed as a backslash and an
> > underscore "\_" in WoMan mode. Is this a bug or a feature?
> >
> > This is from ~M-x woman docker-attach~:
> > #+BEGIN_EXAMPLE
> >   * \\ (two backward slashes)
> >   * \_ (underscore)
> >   * ^ (caret)
> > #+END_EXAMPLE
>
> Please post the man page, I don't have it here.
>
-- 
Meiyo Peng