Indeed, Diagonal walls, Slopes, Same thing to me really.
The engine doesn't crash, but simply doesn't load the world. Which tells me that the engine handles maps in a way that it shouldn't crash unless it's truly a major issue.
Since this is one of toughs issues that are more personal preference
(Having a semi-blocky world gets tiring after a while).
Again, From a map designer's perspective, It does limit what one can do.
There may be work arounds. But they still are annoying to deal with.
but I understand if it's something that's not on the priority list.
Maybe add it as one of toughs polish things later on?
(This is starting to turn into a rambely post.)
Anyways, its just a thought. Nothing that needs to be added in the next update.
Something that would make designing easier.