Ive had a few people try to kill each other. Each time the players were not in agreement so I had to intervene. Technically you do not have to have the other persons permission to try to kill their PC. This is where a mod will intervene and moderate the fight as a fair and unbiased power.
However if you make a name for yourself going around killing pc's at random for no reason XD good luck finding someone to RP with. Also, Im sure there will be IC consequences as well, as you rack up infamy (such as the city guard/bounty/merc's etc being sent after your PC).
Skills DO matter. Again, I would advise to read the
Player vs. Player rules to get an in depth view of how PvP is handled in Mizahar.