SocialProfile's UserProfile implements the social user profile via UserProfile/UserProfilePage.php and a function (wfUserProfileFromTitle) in UserProfile/UserProfile.php which is hooked to the ArticleFromTitle hook. Social profile pages can either be in the User: namespace or alternatively in the User_profile: namespace, depending on the user's personal preference. If the user has chosen a social profile over the standard wiki user page, then their social profile will be on the User: namespace and the wiki user page will be on the UserWiki: namespace.
The UserProfilePage class extends the core MediaWiki Article class and until MediaWiki 1.21, it worked flawlessly. Due to some major changes to core, of which I suspect that ContentHandler is the biggest, this no longer works as of MW 1.21. When running SocialProfile, social user pages do not display _at all_ and standard User: pages cannot be edited (due to the code in aforesaid wfUserProfileFromTitle function, which intentionally prevents editing of user pages since social profiles cannot be edited via ?action=edit but rather via Special:UpdateProfile).
The Apache/PHP error log has entries like this: " PHP Notice: Inaccessible property via __get(): user_id in /var/www/live/w/includes/Article.php on line 1918" which would be totally understandable...if I was trying to access an Article member variable, but user_id is a class member variable of the UserProfilePage class, defined in its constructor function, on line 23 (along with a bunch of other custom class member variables).
Some help in fixing SocialProfile for 1.21+ installations would be very much appreciated.