List of steps to reproduce:

• Visit global preference page (use commonswiki as an example)
• Do some modification, like click both checkbox at Warn me when I leave an edit page with unsaved changes
  
• Goto local preference page
• click the Set a local exception for this global preference checkbox

What happens?:
Local preference could not be modified

What should have happened instead?:
We should be able to set the local value to those preferences, just like it in the "Appearance" tab

I noticed that this issue happens in all tabs except "User profile" and "Appearance", which seems really weird.