The article conclusion is basically that IPv6 extension headers (fragmentation is one of them) are useless on the Internet, which seems pretty reasonable to me.

The article conclusion is basically that IPv6 extension headers (fragmentation is one of them) are useless on the Internet, which seems pretty reasonable to me. They're basically a research tool. The lack of on-path fragmentation in IPv6 is definitely on purpose. It was a mistake in IPv4 and would be silly to replicate in IPv6. The fragmentation header in IPv6 is effectively useless. It can only be done at the endpoints, and if that's the case the application should be doing it, not the stack. Instead IPv6 mandates path MTU discovery, which is the correct solution.