Andy,
On my own Laiti It's a regular thread (clockwise to tighten, counter-clockwise to loosen). The rear one needs a lot of force to tighten it properly, otherwise you'll have drive slip in the lower gears. (the only things transferring the power from the cassette to the hub is the inside of the bearing and the cone of the nut, both of which rely on clamping force to prevent slip)
To remove the nut, don't bother with gripping or clamping the nut itself. My Laiti's wheel nuts don't even have edges, they're just round.
On the other side of the axle there should be a 15mm Allen head. Get a large 15mm Allen key, stick it in with the end pointing towards the rear.
Have someone hold down the front of the bike and put your weight on the Allen key (to rotate it counter-clockwise).
Stand on it, jump on it if needed, the axle is strong enough. Or clamp the key in a large vice, put the bike on top and pull it in the right direction with a couple of people if you must. It should give at some point.
As soon as it loosens up a bit and the nut starts spinning, you should be able to screw it out by hand. (unless they used Loctite or if the thread is damaged). I can literally turn them with 2 fingers because mine have absolutely zero resistance once they're not clamping down the hub, and I haven't even used oil or anything on them.
(I'm using the front one here as an example because it was loose already and I was too lazy to take the bike out of the workstand)
Hope this helps
EDIT : As for the nut itself, you can take it to a machine shop and have it rounded off. It'll look like mine then. As I showed above, there is absolutely no need to use the nuts. I've removed the wheels and put them back on a dozen times already and it always works just fine with the 15mm allen key. Just tighten by hand until it's making contact, then use the key to tighten it properly. It won't slip.
EDIT : Whoops! I made one huge mistake. It's not a 15mm key but a 14mm one.