I would lean more on the side of this being RDM, as the rule regarding gunfights does say that to join a fight you need to have an idea as to which one the traitor is, if people are kosing the other I don't think you have enough information to kill. It maybe a good idea to add to the rule something like 'if both involved players call a KOS on the other you must wait until more evidence is provided before killing either player'.

As for my thoughts on the punishment just a verbal would probably be enough since some would say this is a grey area buts that's just my opinion.

I would lean more on the side of this being RDM, as the rule regarding gunfights does say that to join a fight you need to have an idea as to which one the traitor is, if people are kosing the other I don't think you have enough information to kill. It maybe a good idea to add to the rule something like 'if both involved players call a KOS on the other you must wait until more evidence is provided before killing either player'. As for my thoughts on the punishment just a verbal would probably be enough since some would say this is a grey area buts that's just my opinion.