ZDoom

None, actually. It'd only add a complication to the renderer.

what would be the advantage of having this feature versus just putting the ceiling/floor super high/low?

I'm also kinda wondering if this will be less useful if the glow feature gets extended like it was asked for in the other thread, seeing as we'll be able to do things like fade into mist or blackness when we want to create the illusion of not being able to see the bottom / top of a sector... It'd certainly be less costly than trying to render infinite walls. :V

I've been looking for something like this a long time ago. In the end I just kinda gave up and made a huge column sector specifically for it.

Messing with the linedef code, seeing where someone might be able to add a feature I've wanted occasionally which would, instead of rendering a floor, just keep rendering the walls, infinitely, straight down. That would be good for making bottomless pits and rooms that feel "infinitely-tall".

IDK if I'll feel up to implementing that after this pegging stuff, but I think I see places where it could be done, so I'm leaving it as a suggestion here.