Microsoft has routinely changed the display driver model, breaking backward compatibility. They've also barred print drivers.

> large part of their moat is backwards compatibility

This is more of a religious belief than truth, IMO. They could strong-arm recalcitrant customers, but they don't.

> They could strong-arm recalcitrant customers, but they don't.

They really can't. When the customers have to redo their stack, they might do that in a way that doesn't need Microsoft at all.

These customers wouldn't be able to do that in time frames measured in anything but decades and/or they would risk going bankrupt attempting to switch.

Microsoft has far more leverage than they choose to exert, for various reasons.