1) Instead of the suggested patch (that only fixes one place) I would do:

• Move the logic of auth_plugin_base->get_title() to standalone function auth_get_title() somewhere in datalib or similar.
• Make auth_plugin_base->get_title() to use the new standalone function
• Make all occurrences of "auth.*title" in moodle core to use the standalone function.

2) Or alternatively:

• Leave auth_plugin_base->get_title() unmodified.
• Instantiate auth plugin and use its get_title() method in all occurrences of moodle core

3) Or, also:

• Leave auth_plugin_base->get_title() unmodified.
• Create standalone function auth_get_title() somewhere in datalib or similar.
• Make all occurrences of "auth.*title" in moodle core to use the standalone function.
  (causes logic to be duplicated)

My +1 for 1) above.

Assigning to Jerome, please await Petr's confirmation before doing anything here. TIA!

Ciao

For now I would just hack - base->get_title() to make it search the separate files too
and in 2.0 rewrite the string handling there completely

I personally hate having to instantiate object just to get the title - we do that in blocks for everything and it is a nightmare

For information: the bug appears in three different places, and the code is well written in two other places.

What exactly are we doing for this in HEAD?

What I did was following:
1. Made a stub for new auth plugin
2. Created supposed language files (<MOODLE>/auth/newplugin/lang/en_utf8/auth_newplugin.php)
3. Added strings:
$string['auth_newplugintitle' ] = 'New title';
$string['auth_newplugdescription'] = 'New description';

And it does not work. The only place where string was picked up was plugin title in the admin block (once the plugin was enabled).

In all other places I saw [[auth_title]] and [[auth_description]] instead of [[auth_newplugintitle]] and [[auth_newplugindescription]].