Micky, while I'm not saying I agree with your idea, I AM saying IF your idea were to be implemented, then blocking a player from dueling another player should only be done using the following algorithm:
Player 1 duels Player 2 until he or she gets KO'ed. Player 1 cannot duel Player 2 for the rest of the week. After the week is up, then Player 1 can duel Player 2 again until Player 2 gets KO'ed again. The process repeats itself.
Note: In the above scenario the '7-day cool-down period' starts immediately after Player 2 gets KO'ed by Player 1.
The above scenario MIGHT be helpful to some players who are easy targets however, this is only a possible scenario and is not likely to be implemented, even if somebody like me were to propose it as a possible idea.
So keeping the above in mind, it is always best for a player being dueled often by one particular player to ignore said player. If this doesn't work, then your best bet is to go townless. There are some people who think the constant 48-hour self-KO technique works, however, it only allows for a player to accumulate a limited amount of money before he or she has to bank it before knocking themselves out. A third option, as people have pointed out is to re-skill and then give the dueler a taste of his or her own medicine. And finally, the fourth option is to issue a bounty on his or her head wanted DEAD. If somebody collects the bounty for you and you want more vengeance, then put ANOTHER bounty on his or her head.
I am repeating what everybody else posted in order to drill these tactics into your head, Micky. And on this note, I wish you the best of luck in your travels throughout the Wild West...And wild it is!