I agree with fockmeeard, the whole enemy listing thing is working fine. We just need to encourage more communication between game hosts. Make sure people get the memo when possible (don't outright spam or attack the person in question- we simply need to keep them at bay.)
This system works somewhat, but only somewhat. The leaver is always the person who is not yet on your enemy list, I have a list of leavers almost 40 players long. Also they won't really care, I mean who cares if you are on someones enemy list xaxa lel huehue. But if you have a reputation system people will be a lot more hesitant to just leave on a whim, everyone will know they are leavers which will begin to seriously curb leaving unlike random people enemy listing them. Moreover, new people will see right away that leaving is something you don't do, because it is on their profile.
Now if someone REALLY has to go, lets say your house is on fire, you aren't going give a single crap about your atwar LR system. Thing is most people don't really have to go when they leave, they just say "meh" and leave without a single thought for anyone else. These people should pay for wasting everyone's time. It is also a major complaint by the new players and why atwar has difficulty retaining players since leavers ruin it. Would be wise for the admins to focus on this issue