[plagiat0r]

> But up to this point, that's what the author has been doing. They've setup bind to run on IPv4 and IPv6 but not really the latter, instead blackholing all such requests.

Well, Linux kernel is dual-stacked for more than 30 years now. Every linux VM is dual-stacked unless you deliberatelly disable IPv6 with a kernel boot parameter. And while Linux, and every other modern OS today, is dual-stack, it does not mean that the network you boot Linux with, is dual-stacked. The main criticism is that the algorithm fails to notice that entirely. It is not the "lame-delegation", it is bind9 not being aware of the fact that certain network family is not available, due to outage or just as a starting point.

So while my advice stands, that you should not run any recursive resolver on IPv4 or IPv6 only - sometimes, you have no choice but to do so, as this is the network you are working on. In such cases, this article may help engineers to correctly run bind with either -4 or -6, or abandon it altogether.