A torus just happens to be the easiest way to map a 2D surface so that it gives a sense of roundness and is intuitive for the players. I would really like to play around on a Klein bottle to see how it feels.
Looks like James tested it a few years back, kind of wish I knew about the game then.
Edit: Just for a fun example if a planet were mapped in a klein bottle configuration:
The solid purple dot is your base. You head off in a straight line.
After passing the first north/south splice you notice that east and west have switched positions on your compass. Other than that, everything seems normal. Until you run into your own base again (hollow purple circle). Everything is a mirror image of what it was when you left.
You find it odd, but continue onward. Once again, you cross over a splice and your compass flips directions before stopping at the TƧƎTmall.
If you mapped the same path on a single view of the map, you would end up with this confusing mess, when all you did was walk in a straight line! While walking along the green portions of the path(segments 3 & 4), everything is a mirror image.
