Nathan Gorzelanczyk

That's why Its not a direct issue, because code wise its a lighting issue, its because of an underlying issue,
The same issue as to why half slabs display black. Its because of blocks are treated the same.
Additional blocks are treated different.

Bottom line: Minecraft is code is poorly done. But remember this was one of the first things ever coded by the guy!
If only all of us could do such a great job on our first try! It just needs some refinement and TLC...

Note: That this is a retention issue. Like Glow-stone holding sunlight.

1) Recreate it by making a dark room BLl0 SL0 RL0
2) Place Glows-tone, Note light, BLl8 SL0 RL8 (0 Sunlight)
3) Place Remove a block allowing sunlight, Note light, BLl8 SL8 RL8 (8 Sunlight)
4) Place block back allowing no sunlight, Note sunlight does not change, BLl8 SL8 RL8 (8 Sunlight)

Torches do not hold retain light.

Before a block is updated its Sunlight or Lack of Sunlight is retained.
When the near block is updated so is the Sunlight.

This is why when a Block is removed the black lighting is also removed.

Why glowstone? Well simply put blocks are treated different than something like a glass panel, pot, or sign.
Hope this help in understanding the issue.

Also note: In real life thinner glass lets more light through.

This is not a bug.
Understand that the lighting is per block area.
The block area is 1 brighter because of its location to the light.
Its actually closer to the light therefor is brighter.

Mark This as Duplicate.

Keep MC-119 Going downward through solid blocks, causing suffocation, death of entries, and entities escaping
Keep MC-2025 Going forward through solid blocks, causing suffocation, death of entries, and entities escaping

Mark This as Duplicate.

Keep MC-119 Going downward through solid blocks, causing suffocation, death of entries, and entities escaping
Keep MC-2025 Going forward through solid blocks, causing suffocation, death of entries, and entities escaping

This is related to my post of,,, MC-11349
https://mojang.atlassian.net/browse/MC-11349
which is aparently a duplicate of this according to mods.
https://mojang.atlassian.net/browse/MC-2025
These are also related to it MC-10, MC-18, MC-119, MC-1029, MC-1524, MC-2025, MC-2037, MC-3140, MC-3753, MC-4707, MC-5187, MC-5230, MC-5369, MC-5401, MC-6115, MC-6393, MC-6396, MC-6398, MC-6465, MC-6653, MC-6707, MC-7392, MC-7462, MC-8390, MC-8707, MC-9039, MC-9393, MC-9476, MC-9483, MC-9503, MC-9525, MC-9540, MC-9568, MC-9626 , MC-9635, MC-9742, MC-9753, MC-9772, MC-9777, MC-9805, MC-9838, MC-9894, MC-9926, MC-9976, MC-9988, MC-10012 , MC-10116, MC-10157, MC-10181, MC-10229, MC-10231, MC-10268, MC-10311, MC-10370, MC-10422, MC-10552, MC-10725, MC-10797, MC-10894, MC-11009, MC-11022, MC-11052, MC-11086, MC-11203, MC-11252 ....

This is related to my post of,,, MC-11349
https://mojang.atlassian.net/browse/MC-11349
which is aparently a duplicate of this according to mods.
https://mojang.atlassian.net/browse/MC-2025
These are also related to it MC-10, MC-18, MC-119, MC-1029, MC-1524, MC-2025, MC-2037, MC-3140, MC-3753, MC-4707, MC-5187, MC-5230, MC-5369, MC-5401, MC-6115, MC-6393, MC-6396, MC-6398, MC-6465, MC-6653, MC-6707, MC-7392, MC-7462, MC-8390, MC-8707, MC-9039, MC-9393, MC-9476, MC-9483, MC-9503, MC-9525, MC-9540, MC-9568, MC-9626 , MC-9635, MC-9742, MC-9753, MC-9772, MC-9777, MC-9805, MC-9838, MC-9894, MC-9926, MC-9976, MC-9988, MC-10012 , MC-10116, MC-10157, MC-10181, MC-10229, MC-10231, MC-10268, MC-10311, MC-10370, MC-10422, MC-10552, MC-10725, MC-10797, MC-10894, MC-11009, MC-11022, MC-11052, MC-11086, MC-11203, MC-11252 ....