Many of the "IPv6-isms" come from the fact that renumbering networks is a big PITA and so IPv6 was built with the pipe dream of "change the config on the router

Many of the "IPv6-isms" come from the fact that renumbering networks is a big PITA and so IPv6 was built with the pipe dream of "change the config on the router and the entire network renumbers itself", like the flick of a switch. It was optimised for the least used case. IMO they should have just increased the address bit size to 128 and be done with it. One of my own annoyances is the fact that local subnets have to be /64's (you can make smaller subnets but it breaks certain things) and ISP's are supposed to deliver a /48 or /56 to subscribers but some ISP's will only hand one /64. So if you want to create 2 separate networks in your home you're screwed.