A Hacker News thread discusses killer whales (or orcas) and their behaviors, sparked by an article about them grooming each other with kelp. Commenters share interesting facts, including their unique "salmon hat craze" and historical role in assisting Australian whalers. There's debate about the accuracy of the name "killer whale," with some arguing "orca" is preferable and "killer" is unfairly prejudicial. Some users point out that Orcas are technically dolphins and whales. Others debate the intelligence and hunting behaviors of orcas, with discussions on whether they "offer" food to humans and if some of their hunting tactics could be viewed as torture. One user points to other examples of apex predators (namely sharks) who've been known to offer food to humans. Overall, the conversation highlights the intelligence, complex social structures, and diverse behaviors of these fascinating marine mammals.