Wikimedia Bugzilla is closed!

$ w3m -dump http://www.mediawiki.org/wiki/Manual:\$wgSecretKey|grep always
             This should always be customised in LocalSettings.php
This should always be customised in LocalSettings.php

But nowadays one only sees $wgProxyKey in LocalSettings.php.

In DefaultSettings.php, one sees these lines mashed together,

/** This should always be customised in LocalSettings.php */
$wgSecretKey = false;
/** big list of banned IP addresses, in the keys not the values */
$wgProxyList = array();
/** deprecated */
$wgProxyKey = false;

Well if it is deprecated, then don't use put it into the
LocalSettings.php produced.