I feel that 4J should make an update that does nothing but fixes a crap ton of bugs, you know, so the bugs that were added in lets say TU5 and weren't fixed in TU6 can be removed from the game, and so you don't suffocate from glitching into walls while walking down a hallway. And then the lighting issues.
I wonder. Is that issue caused by a fixable bug, or hardware problems? I am not sure.
It appears to be software related, I've only witnessed 2 different types of this lighting issue instance.
The first is where leaves on harvested trees that naturally deteriorate do not necessarily trigger the lighting update to alter the shaded region below as they allow sunlight to pass through, so I often see the shadows of harvested trees long after the leaves have deteriorated in some areas.
The second is where the timing issue with inter-chunk updates does not execute in a timely fashion, which leave lighting along the chunk borders distinctly different when light level in the area is suddenly changed. This between-chunk timing issue has also impacted a lot of redstone mechanics. Maybe have the game execute a chunk border check immediately after there is a block update along a border within that chunk at the same Y elevation (so as to minimize the amount of processing update checks for best efficiency)?
I'm not sure that I've seen other causes for patchy lighting issues however.....
IDK if anyone else thought of this but one torch would ruin spelunking in minecraft for me because all you really need is one torch to explore. A simple fix could be to just make the torches so they run out.