As part of bug 46306, an option was implemented to disable UniversalLanguageSelector (ULS) on a per-user basis. I believe the addition of this user preference is a temporary measure that should eventually be reverted.
Adding a user preference contributes to (very visible) user interface clutter and should only be done as a last resort.
Version: unspecified
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=48535