I think that open world dueling would be awesome, but I can see how it could be a problem in cities. Every other MMO I have ever played had this function and I never saw any of the problems that I see people complaining about on this thread. In my experience if someone challenges you to a duel and you decline they generally just run off and do something else. They should allow it outside the cities and maybe only allow dueling in cities in a fighting arena in each major city. Adding duels would make yet another way that players could interact with each other and adding the fighting arena would make the cities a lot more interesting. I fully support this feature especially if an auto-decline option was added for when you just don’t want to bother with it.