Illustrated here: https://youtu.be/gyTjR8eXuug
Without naming any names, this was being done by a whole caravan of veteran players, and when I complained that it was exploitive of map geometry, the majority insisted that it was not against the rules as it can be done by both teams, one even said something along the lines of "if you don't like it, blame Yosh."
Personally I think this should be considered a glitch and hopefully patched to make it technically impossible, and in the meantime it would be nice if the community could come to a consensus as to whether or not it's a kickable offense. If the community collectively decides it's allowed then I guess I'll live with it, but I can't imagine that this is the intent of the map maker as it completely defeats the point of having "walls."
You can make the point that aircraft can overcome the walls, but I'd counter that by saying 1) Aircraft are loud, and 2) Aircraft cost a lot more than 300/350 credits for the privilege.
Thoughts?