IIRC, the 'M' signal alternates (with every frame?) to reverse the voltage across pixels to prevent a DC bias damaging the pixels (by some electrolytic effect?).
I can see this works for a static image, but what would happen if you had the screen being inverted at exactly the same rate?
Would this result in a net DC bias and ensuing damage?
Or does M spend 50% of the time in each state for each line of pixels?
A mate of mine reports 'screen burn' on some LCD monitors at work. I thought that only happened in older CRTs. Perhaps 'M' wasn't exactly 50% duty cycle for those LCDs.
K.