I've tried it various ways over time, and settled on the approach whereby each (potentially-modified) key in a command key sequence is written in standard Emacs notation and wrapped in <kbd> markup, and anything else the user types (commonly at a prompt) is wrapped in backticks.

This distinguishes the command key sequences from other typed text, which I feel makes for the most easily-comprehensible output.

Any concerns about the difficulty of entering the markup would seem to be virtually moot in a forum where *every single person writing an answer uses Emacs*, given that modern web browsers have extensions to allow you to edit textareas in your editor of choice. Providing some common support elisp for users seems like a Thing We Can Do<sup>1</sup>.

I agree that the kbd tags should be styled for readability. FWIW, my user style sheet for SO/SE uses the following:

<!-- language: none -->

    kbd {
      background-color: #e9e9e9 !important;
      border: 1px solid #999999 !important;
      font-weight: bold !important;
      font-family: Courier New, Fixed, monospace !important;
      font-size: 9pt !important;
    }

which for me, renders like so:  
![enter image description here][1]

or at the default font size:  
![enter image description here][2]

The following is an [example from SO][3]:

<hr/>

So first, check to see if you have an existing file.

<kbd>C-h</kbd><kbd>v</kbd> `user-init-file` <kbd>RET</kbd>

By default it will show you a file path ending in `/.emacs` (even if that file doesn't exist), but on the (unlikely, in your case) offchance that it ends in `/.emacs.el` or `/.emacs.d/init.el` then it would mean that you have an existing init file at that location.

Load that file with the appropriate one of the following:

* <kbd>C-x</kbd><kbd>C-f</kbd> `~/.emacs` <kbd>RET</kbd>
* <kbd>C-x</kbd><kbd>C-f</kbd> `~/.emacs.el` <kbd>RET</kbd>
* <kbd>C-x</kbd><kbd>C-f</kbd> `~/.emacs.d/init.el` <kbd>RET</kbd>

Or you could load it regardless of where it was with:  
<kbd>M-:</kbd> `(find-file user-init-file)` <kbd>RET</kbd>

Then you can simply add that line of code to the file:

<!-- language: lang-el -->

    (setq visible-bell 1)

Save the file:

<kbd>C-x</kbd><kbd>C-s</kbd>

And the next time you start Emacs, it will use that setting.

You can also evaluate the setting immediately by typing <kbd>C-x</kbd><kbd>C-e</kbd> with the cursor after the closing parenthesis.

<hr/>

<sup>1</sup> For starters, a minor modification of [Malabarba's answer][4] to https://emacs.stackexchange.com/questions/2206/i-want-to-have-the-kbd-tags-for-my-blog-written-in-org-mode gives us:

<!-- language: lang-el -->

    (defun my-insert-kbd (key)
      ;; Based on https://emacs.stackexchange.com/a/2208/454
      "Ask for a key then insert its description using <kbd> markup.
    Will work in org-mode or in any mode that accepts plain html."
      (interactive "kType key sequence: ")
      (let* ((is-org-mode (derived-mode-p 'org-mode))
             (output (if is-org-mode
                         "@@html:<kbd>%s</kbd>@@"
                       "<kbd>%s</kbd>")))
        (if (not (equal key "\r")) ;; empty key
            (insert
             (format output
                     (mapconcat 'identity
                                (split-string (help-key-description key nil))
                                "</kbd><kbd>")))
          (insert (format output ""))
          (forward-char (if is-org-mode -8 -6)))))

    (global-set-key (kbd "C-c k") 'my-insert-kbd)


  [1]: https://i.sstatic.net/UR1xF.png
  [2]: https://i.sstatic.net/kKlp8.png
  [3]: http://stackoverflow.com/questions/10545437/how-to-disable-the-beep-in-emacs-on-windows/10545955#10545955
  [4]: https://emacs.stackexchange.com/a/2208/454