Weird that you can't reproduce it! My computer is weird with brightness, so it might be something to do with my settings. But it honestly wasn't that intrusive, and wasn't visible in the platforming scenes. What I seem to see is that in the dialogue/story scenes, you sometimes have pauses between lines of narration instead of a line immediately following the previous one. That last line was still visible after it seemingly faded to transparency in this scenario. Here's a snapshot I just took towards the end of the game.