Someone else recently asked much the same question and got much the same answer.
There's also another answer to this question,depending on exactly what do you mean by 'enemies in the enemy/home kingdom'?
You only score points against the clan you were drawn against in the clan versus clan event, but you will get points in this event and any other events that are running at the same time in which involve killing troops according to the information about that event.
So you only score points according to the formula against your designated clan, which I think you will find isn't double.
Its the same if you are at home away for killing, but double away for some other categories.
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