This is how it looks in the editor. The selected sector is where I stand in-game and where the cutoff begin.
Notice how the light suddenly drops past a certain light level and the smooth gradient effect breaks. For what it's worth, sprite brightness seems to be correctly respected, it's just the sectors themselves that are rendered inconsistently with what's expected. Somewhere around light level 100 is when the brightness starts to go off in both directions.
Loaded this with a gameplay mod because that's what the test map is part of, but the mod itself does not do sector light manipulation whatsoever, so it's not a mod issue. Just to be sure I loaded this in vanilla doom too. Download for just the map. Turn right at start, enter red teleporter.
