Also, why does Firefox let an extension decide whether it is uninstallable or not? In the OP, commenter WladimirPalant says that's a side effect of a Firefox f

Also, why does Firefox let an extension decide whether it is uninstallable or not? In the OP, commenter WladimirPalant says that's a side effect of a Firefox feature which allows plug-ins to be registered via the Windows Registry. But disabling will have the exact same effect: the plugin is not loaded.