Hello everyone, this is my first post here.
This thread is very interesting. I am in agreement with most of you that McLaren have done nothing that is illegal. They have taken at least one dial and have situated the control at the driver's fingertips. I am sorry if this is a duplicate post, but my observation is that in placing the control where they have, McLaren have changed the nature of the device from a variable device that is passive through cornering into a dynamic device that is active during cornering and is being used to control the car. It is quite a fundamental change in the way that the device, be it engine mapping or differential, contributes to the amount of control that the driver has over the car.
There are some on-board images of the Malaysian GP on YouTube, when watching the BMW and Toyota drivers, it is possible to predict whether there is a left or right handed corner approaching. With some of the other drivers, it is possible to see extra hand movements without being able to determine what they are doing. Other drivers, like Williams', appear to be just hanging on as they go through corners.
McLaren and Ferrari have been very clever, but they have given the driver greater control over the way that the car understeers and oversteers through corners.
Williams and proud of it.