There is something wrong if you are still seeing the braces, and if not then there is nothing wrong
Make sure you run /admin/purghcaches.php
between changes (in fact run it right now to check)
This
public_html/domain/lang/moodle.php
should be at least
public_html/domain/lang/en/moodle.php
But moodle.php seems wrong, that should be whatever the autorisation plugin should be in the same form as the plugin name, so if you were modifying ldap authorisation (not something I reccomend),
You would have
public_html/domain/auth/ldap/lang/en/auth_ldap.php
And the language stuff goes in there.
Your call to getstring will need to name the component it is linked with get_string('gender'','auth_name');