Hi A33Zab,
As I recently understand from the 757/767, despite the 'interconnected' yokes, the possibily of splitted RH/LH Elevator surface control doesn't seem to be a good idea either.
I don't know if you are referring to some incident (link?) which I don't know about.
On the TriStar we could split the Capts & FO's load paths to the L & R elevators and L & R ailerons respectively, so it was technically possible to fly each side independently. They were only split if we had a control jam on one side. PFM.
How would it determine which input to follow?
In that case, you'd have to do as Airbus now do - only one pilot at a time flies the plane.