You may be technically correct SD - which I do not doubt. But the realities of fencing nowadays are somewhat different. I've never seen double fenced boundaries and certainly don't have any on my land where my livestock fields adjoin my neighbours.
If my cattle get over a joint fence into my neighbours sheep pasture, then it's up to me to raise the fence, or put some more more posts in to prevent it.
If my cattle get onto a neighbour's cattle pasture, then again it's up to me to tighten the barbed wire or whatever, but if his cattle are straying onto mine then I expect him to remedy the situation. We certainly don't each maintain a separate fence on the same boundary.
In reality stapling stock netting to an existing fence is not causing damage and few people would take anyone to court for doing it. It would be a civil, not criminal matter and the costs would be prohibitive. The same with a horse getting its foot stuck in stock netting. Difficult to prove whose fence was responsible as its foot had to go through the wooden fence first, and again would have to be sorted out in a civil court.
It's not a perfect world and accidents happen. I just make sure my insurance against the unforseen and unlikely is up to date and use my common sense.
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