Yup, just checked out the changelog:
10-23-2006: 7.1 Change: Moved all portal box language strings into a single language file. Altered all of the cache builders to convert the language strings when displayed instead of storing the converted string in the cache. This was a necessary change that will allow us to bring back user selectable languages with a bit more work.
10-23-2006: 7.1 Change: Added a new field to the user_profile table to store the user selectable language. Modified the main ubbthreads.php to load the user selected language files. Also modified the language editor in the control panel so the admin can check which languages the user can choose from.
10-24-2006: 7.1 Feature: Finished with all modifications to bring back user selectable languages.
The feature for users to select their own language doesn't exist in the current codebase; it will be back in 7.1.