Though it is not clear if insects are phenomenally conscious (and so if they can suffer), I think that we should take precautionary measures now to avoid moral catastrophe. Expert seem to be divided on the question of insect consciousness.

Are experts really divided on the question of insect consciousness? Or is it that some are pulling some sleight of hand by redefining "consciousness" to refer to easier questions such as planning and spatial awareness ("primary consciousness") which consist of capabilities little more advanced than has a program like AlphaGo or a micromouse entrant?

This point seems like it deserves to be more directly addressed, given how important it is. If insects are not conscious (which seems like the far more likely case) then all the rest of this doesn't matter at all.

Relatedly, insects are harder to fully kill or render unconscious in a conclusive way. This probably makes it more difficult to find a more humane way of killing insects. This is because insects have a less centralized nervous system (think of the fact that cockroaches may survive for a while without their heads). This may mean that isolated parts of their nervous system might still continue to function and potentially register pain even after massive bodily damage.

For instance, this is fine if the "isolated parts" lack phenomenal consciousness, which is even more likely than whole insects lacking it.