Raised beds

I too thought you avoided moss in compost (because P said so - but who takes any notice of him anyway?) But they say sphagnum moss is desirable for all sorts of things, especially retaining moisture. What's the difference between the scourge of my lawn and sphagnum? Also, our top lawn (I use the term 'lawn' very loosely) is more moss than grass and all the mowings from this goes into the compost bin and after 1-2 yrs it is wonderful, quite dense, black gold with no signs of unrotted moss. I suppose the only way to find out is to try it. I've also considered using moss in a bean trench to retain moisture, not done it though.