Yeah, I saw that when I was doing textures. Looks like it could be used to extend lanterns and ceiling torches down from a high ceiling.
I just dug to bedrock in less than a minute, in a brand new, perfectly normal, world.

2 things that are permanently coded into the game and annoy me are,
1: I can't change snow or graveyard biomes, or make any other biome come within 20 blocks of the surface.
This seems to be different in the most recent version of the game though.
2: I can't make swords effective against blocks, or make tools effective against mobs.
If I could I'd only need one type of tool to one hit kill/break anything.
1. Junk-Jack-Wiki2. The world is big, 256 blocks high and 768 across.
3. Who is John Galt?
4. Lack of objection does not indicate consent.
5. We scream, we shout, we wail, we cry; but in the end we all must die.