Sven Groot wrote:
It would exclude things like speech recognition and other accessibility software though that simulate user actions for good reasons.
And it would make the nay-sayers go "M$ forces people to buy new keyboards".
Not necessarily - software that simulates input could in itself be protected with DRM, and interact with windows TPM systems.
What you are asking for is already there. The UAC prompt is in a trusted process that can only be accessed by other trusted processes. The only way a piece of software, malware or accessibility software, can touch it is if it already has fully trusted and elevated.
In that situation it could do anything it wants without triggering UAC anyway.