I can't get mesh displacement to work on a population of, in this case, peat blocks. In fact I can, but the mesh is deformed on the base object, and even with a transform shader set to world, it won't spread the displacement across the pop in world space. Too bad, as I wanted to have all slightly different blocks.
So, here's my feature request; please, make this possible. It would be very handy, just like world opacity, to have world mesh displacement.