Found this while testing r97296. Since I wrote the exact steps to reproduce this in IRC, here are the logs:

<hexmode> installed and created default LocalSettings.php
<hexmode> User:Test has no content [15:59]
<hexmode> Log in as Test
<hexmode> create User:Test with content "blah"
<hexmode> Change gender to male [16:00]
<hexmode> added $wgExtraGenderNamespaces line to LocalSettings.php [16:01]
<hexmode> Visit User:Test [16:02]
<hexmode> redirects to The_man:Test
<hexmode> no content
<hexmode> Remove line from LocalSettings.php [16:03]
<hexmode> Return to User:Test
<hexmode> shows content "blah"

Note that the exact line I put in LocalSettings.php was:

$wgExtraGenderNamespaces[NS_USER] = array( 'male' => 'The man', 'female' => 'The lady' );

Niklas told me this was a mis-communication and that I should have used 'The_man' and 'The_lady' instead.

Version: 1.18.x
Severity: normal