From the same article you posted:

Denying that crabs feel pain because they don’t have the same biology is like denying they can see because they don’t have a visual cortex

when he brushed acetic acid on their [prawn] antennae, they began grooming the treated antennae with complex, prolonged movements of both front legs. What’s more, the grooming diminished when local anesthetic was applied beforehand.

He then turned to crabs. If he applied a brief electric shock to one part of a hermit crab, it would rub at that spot for extended periods with its claws. Brown crabs rubbed and picked at their wound when a claw was removed, as it is in fisheries. At times the prawns and crabs would contort their limbs into awkward positions to reach the injury. “These are not just reflexes,” Elwood says. “This is prolonged and complicated behavior, which clearly involves the central nervous system.”

Whether or not the subjective experience of pain is emotional or not is irrelevant. Obviously insects use a radically different mechanism for sensing external stimuli, but does that make human pain objectively superior? When it comes to arguements regarding whether or not insects feel pain, I feel like these arguements are often motivated to sensationalize the human experience, as if it is somehow more special that everything else.

To me it's obvious why we do this. Human pain is the only pain we know. That's simply a matter of our subjective bias. But that doesn't justify protecting some animals while abusing others because they don't produce the emotional response we expect them to. We all have the same common ancestor. Every species still alive today is equally successful, and equally critical for their respective ecosystems.

While I am by no means a vegetarian, I find sentiments that justify protections for animals based on cognative performance hugely hypocritical. We should be protecting our ecosystems regardless of what inhabits them, not just the animals that seem the most human. And when it comes down to it, eukaryote cells, plant or animal, are remarkably similar on the cellular scale. In this context, even the vegetarian arguement is invalid. We can't synthesize every amino acid. We can't fixate nitrogen. We're specialized at consuming other life to survive.

As far as I'm concerned, if any species is objectively superior to any other organism, its algae. They support pretty much all life on earth.