There are some HPC environments that use Kubernetes but they likely use custom schedulers optimized for batch workloads (e.g. https://github.com/volcano-sh/volcano).

"containers" are often used but not always docker containers. HPC environments I've seen will often use container primitives (e.g. cgroups, namespaces).

There's a lot you can learn with managed Kubernetes and it's a great place to start. You can learn a lot of the parts of Kubernetes with running through https://github.com/kelseyhightower/kubernetes-the-hard-way or reading https://www.amazon.com/Kubernetes-Running-Dive-Future-Infras...

I'll email you to follow-up since tracking HN comments isn't a great way to have a conversation.