On certain wals there seem to appear those tiny sparklies that run along the upper/lower end of the textures. I have applied a screenshot of Memento Mori's map 10. It also happens in a bunch of other custom maps, including one that I'm tinkering with.
It happens on random walls, no matter if the texture is dark/light. And it seems not to happen at all in the original maps. Even if it does, the sparklies are SO tiny, you need a magnifying glass.
Sloppy nodebuilding or Zdoom's fault?