This bug is more clear in the screen shots I attached. Seen from the top of stairs leading down to the floor of a corridor, the entire corridor is visible. From the floor of the corridor, visibility is maybe ten blocks. The corridor is at bedrock level, so any "gloominess of depth" would be in play, but I consider this a bug because that doesn't make any damn sense.
I'm using Mac OS X as a client to a Linux server. I've seen this behavior in 1.3.2 and 1.4.2.
Corridor seen from bottom of stairs
Corridor seen from top of stairs.
I've seen this happen too, and I wish it were fixed. Alternately, if there were some way for the player to produce the same structure, that would be neat. I don't like that the generated world contains things the player couldn't create.
I think if I can see the floor from the ceiling, I should be able to see the ceiling from the floor.