Multilang filter works with the field in Manage Authentications. I use that myself. One possible problem might be that the field size is too small to store your text for 6 or whatever languages you have. If that is the case, some if not all languages would display text combined with multiple languages, truncated in some odd place. More likely, there is an error with html tags. If you are using WYSIWYG
editor, it probably mangles your input. It is a source of problems for many people using multilang filter and there are some alternative versions of it as the result.
Well, the text from the input field is kept in the database and fetched from there into some variable then displayed after being run through the multilang filter. You need to find the line in code that displays that text and replace it with a line that recalls a string from the current language pack. You can find examples of that in the same function, I am pretty sure. If you have problems locating that, feel free to contact me by email.
Now, the tricky part is to get the strings in the language packs. I presume that you would prefer to be able to use the web interface to edit those strings (as local changes) since that makes things simpler on the long run. Besides, adding new strings to a language pack poses some issues. I would find an existing string that it not used on your site. It does not have to be in the moodle.php file. Just browse through your lang pack to find such a thing. Note its exact name and the name of the lang file it is in. Customize it for your needs in any language you want and recall in the hack above. You can store the reference to it in the admin panel, so it is documented.
This should work. You will just need to transfer this hack when you switch to a new major version of Moodle. If your Moodle is installed from git
, you can merge minor updates without loosing your hack.
By the way, a request to move those instructions to language packs was turned down, cf. MDL-4477