Basically, it is possible to teleport outside the world (for example at x=40M and z=40M). Eventhough it is not possible to do it directly with "/tp @p 40000000 ~ 40000000", it is possible to get to this situation by using relative telepot.

What I expected to happen was...:
To get an error message because I shouldn't be able to teleport outside the world.

What actually happened was...:
I teleported outside the world, so I got the "Illegal position" message and got kicked from the world. When I tried to open the world again, I was still outside the world, so I got kicked one more time.

Steps to Reproduce:
1. Execute "/tp @p 20000000 ~ 20000000";
2. Execute "/tp @p ~20000000 ~ ~20000000".

I remember that before 1.8 this issue was already fixed (Minecraft automatically checked if with relative teleportation you would go outside the world, and if so, deny the teleportation), but for some reason now there's this bug again.