I once fell asleep in a climbing harness I was using as a deer stand. I believe I was asleep for ten minutes or so. I didn't die. I also don't believe that modern arborist saddles are a problem, and also agree with
@Steve Connally that the cheesy webbing fall arrest harnesses could very well be a serious problem. Even if they didn't cause suspension trauma, I don't think highly restricted blood flow to your legs would be a good thing.
Actually nice to see the subject revisited, though. Luckily, comfy harnesses are what arbs want, and what the OEMs are trying to produce. All they really need to work on is an air conditioned one with a built in waffle iron.