I actually don't know how Deli can draw fencing across the stairway and have it not be deleted, because stairways always conflict with walls so there can only be one or the other. It's a part of the game rules and moveobjects doesn't affect this whatsoever. I suspect it's somehow related to that her room is according to the game, not an actual room but a deck with walls (it's treated differently by the game), which is why she suffers from the roofing clipping through the walls. If the room is considered a proper room, roofing clipping through walls will be automatically deleted.
You can do what she did but draw a fencing around the tile in front of the staircase though, as that tile is the one that has to be free for the staircase to be functional. Once that's done you can remove that fencing and recolor the flooring to your liking.
