Anyhow, I think we are fundamentally in agreement that all of the spokes in the wheel are in tension at all times. I am not an engineer, but I did run this bit by an engineer. He was in agreement that the fact that the bottom spokes are under less tension does not mean they are supporting the load via compression.
At best, the passage is a bit misleading; none of the spokes on a bicycle wheel are ever in compression (or as Brandt rightly claims, they would buckle). Claiming that the reduced tension (again, correct) supports a "compression load" is misleading.
Sorry I can't stick around for further discussion; I'll check back later.