Absolutely it is. But still, the colons and brackets often make things awkward, leading not only to such compatibility bugs, but to general usability issues. Colons and brackets are just too overloaded within both destination specifiers (e.g. for ports, paths...) and shell syntax, and probably other things, where as the dot '.' rarely is.

I'm an avid user of IPv6 by the way, I don't share a lot of the criticism. For me personally it's a net positive. But this is a wart where I wish they went a different direction.