Seems you can remove walls by the map edge (using deconstruct) but when you use the Remove Floor command it seems to do the same check as if you are placing floors, thus preventing floors from being removed near map edges.
I think the actual bug is that it shouldn't be spawning walls (or buildable floors) near the map edge outside the buildable area.
This bug still exists as of A15.
Behavior confirmed, not really a game-busting bug, but perhaps allowing for removal of structures but not building outside of the area?
Bug confirmed. I have listed it on Mantis here: https://ludeon.com/mantis/view.php?id=2628 Thank-you for reporting this.