Resolved in 13w02a
Or at least it was supposed to be, it still won't work with a single player, and a repeater. Making it useless still.
Still seems like a bug, if I was in creative mode, got all the achievements by spawning items, and then go to survival mode, the achievements are still there.
The wire may have updated instantly, but you would expect the one that is closer to be updated first, because both repeaters are set at the same delay. In the first picture the first repeater turns on, then the second repeater locks it. In the second picture the second repeater turns on, and the first repeater never turns on. In both cases the repeater connected to the lamp is closer, and both repeaters have the same delay. So it's inconsistent that the lamp lights up in only one case.
Resolved, I get why it does this now, not a bug.
Here's another picture making the oddball repeaters more noticable.
Minecraft version 13w01b world save file, that shows this bug in action.
I think this is still a bug, it should really be updating those in order of signal strength from the source, so in both cases the lamp should be on.
I did some testing on this, I confirmed that a comparator block updates a dispenser rapidly and causes it to fire. I added a screenshot to show this bug in action.
A redstone lantern is a solid block, when you put a redstone torch next to it you turn on the light, but do not power the block. When you run a wire, or repeater into it you turn on the light, and power the block, causing it to give off power to the sides. This is most likely intended, because every other solid block has this property, including note blocks, and dispensers.
He's right though, it should propagate a signal like a pressure plate does for it to be useful.
Even if it was emitting 1 charge(the lowest signal level), a repeater should still be able to pick it up on the other side of the wall, so this is a bug.