yeah I think ground zero should be feared by new players. It shouldn't be safe one block from a road. that also allows players to play it close by jumping the line for safety all too often.
People who dance on the line can simply be shot.
Combat that starts in south/city can be continued outside.
That doesn't mean of course you can follow someone and kill them half an hour later because they were in the south once.
So yeah, dancing around the 0/city line, simply means you are flagged for PvP.
In the end it's common sense, if you are on the very edge of the city with your toes almost hitting the city, don't come bitching if you get shot, not because it is allowed, but because it would actually be hard to tell.