While there is not a whole lot of substance in the article, it's not unreasonable to assume that insects are capable of nociception. Even single-celled organisms like amoebas can show an injury response, because it makes sense evolutionarily to be able to react to harmful environments. That insects produce some of the same neurochemicals as higher animals is also not surprising - these pathways have been evolving for a long time. Of course, they tend to grow in complexity with the rest of the organism.

What the article gets wrong, I believe, is the ethical dimension. I would make the argument that for an organism having nociceptors and pain responses is not enough to assume capacity for suffering as we know it (which granted is always a big caveat). I could write a program for a simple robot that shows a pain response. That's not enough.

The missing component here is a brain capable of suffering in a meaningful way. Personally, I suspect there is no convenient limit value for this as you go up the ladder of brain complexity. It's just one big muddy gradient. Where a person draws these lines is almost arbitrary: for example, I don't really care about the well-being of a moskito, but starting with spiders I feel increasingly guilty for not helping them when they're in trouble.