I made a trading room and I put lava all around the room so players were unable to /jump. I'm a 100 donor so I tried and I can tell you that even with /god, you can't go away if you do it correctly [EDIT] : If someone trespass on your island, you can ask a mod to /sudo him away.
Oh I forgot to say using jump with /fly and without it yields very different results. You can jump horizontally through walls without fly but if you have it on you just bounce. I was at megadorkvikkis island for hours trying to test all possibilities.
