If you want to stay up-to-date with modifications in between official releases, I think your best option is to subscribe to the SVN mailing list which emails you every time someone modifies the code (instructions on mediawiki.org). Beware, however, that there are a *lot* of modifications made (many of them just updating language files, but you get an email anyway). Also, using code which isn't an official release means you are testing possibly extremely buggy code and it isn't recommended for real world usage (it generally works fine, and major bugs are fixed pretty quickly, but there are no guarantees). That said, I don't think what you're seeing is a change in code. I think it's just a configuration option in LocalSettings.php, I can't remember what it's called, though.