When you successfully throw a net at an opponent, he is restrained until he uses his action to break the net (DC 10 Strength Check) or until slashing damage is dealt to the net (AC 10, 5 HP).
While the rules say that you can damage a net without its prisoner (to liberate a netted friend, for example), the contrary is not specified.
Considering an enemy with AC 10 or higher, can you hurt them with slashing damage without damaging the net ?
There isn't a specific mechanic within the rules for the net taking damage when the prisoner is hit.
The GM will have to decide based on circumstances.
This is a rare case of there being an actual useful difference between slashing, piercing, and bludgeoning weapons. I would rule, in this case, that slashing weapons would damage the net, but piercing and bludgeoning would not. Any weapon can damage the target, unless you're taking special care not to. Slashing weapons, I would rule, also damage the net.
