

He gives some examples of firmware updates being pushed out to Internet-connected Brother printers to cause them to stop accepting third-party ink cartridges
This is not supported by the references in the linked article. They only talk about the printers refusing to do automatic registration with third-party cartridges.
No, human language.
Well, they’ve also been used for code, but that’s still designed for humans. I doubt you could use something off the shelf for binaries.