Stateless desktop is a feature. Application state is something I have to mirror in my head to prevent applications from doing unwanted and surprising things.

IMO, even the clipboard metaphor is too much state. We already have the selection highlight, which has the nice benefit of being directly visible. This should be reduced to a single global selection highlight. Then copy and paste can be replaced by "duplicate highlighted selection here", eliminating the possibility of forgetting what's in the paste buffer.