With or without the map editor. Here's an example: Note that it is impossible to drop any troops on the top or left sides shown in this base. I just made it as a proof of concept. Since the bug only exists on two sides, however, it is of limited use. If it were possible on all four sides, one could easily make an impenetrable island.
Here is a better example of how this could be abused: Fortunately, however, it turns out that troops will walk around the outside of the map to get inside. So although it is impossible to deploy troops along the straightedge shorelines, they do not work as walls. So people may try to cheat using this however it is not too bad of an impact. This concludes my experimenting with this and I will now be reverting to a normal layout. In the interest of full disclosure, here's how it's done: Select a row of walls, say 20 long. Point it towards one of the edges and drag it farther and farther out, until you see it pressing out beyond the normal boundaries. Watch for the normal shoreline to change to a straight line - this is an indication that you have gone as far as you can - push it one more tile and the game will crash. Once it's there, lift your finger. Now skipping the end piece that you want to leave in place, select the adjacent piece and move it back into the normal map area. Now you can use the row of walls to repeat. In the above example I did this for two rows of wall pieces all along the top and left sides. I will be reverting my map to a normal layout very shortly. Please don't cheat.
Before people start saying, "since it's available to everyone, is it really cheating?", yes it is, the game wasn't designed to build your island this way, and you have to use trickier of the system to acquire that side like this. It's no different than stacking walls. Nice find Raptelan, and thanks for being honest in the process.
Just need to tag @Sir Bugsalot , @Lynsey [Midoki] , @AngryBeard and @Chris [Midoki] Good find Rapt.... Hope it gets fixed soon