Murray : (...) I believe that you'll love gtkmm if you love C++, and that gtkmm is a better role-model if you're learning C++. (...)
I'm not sure about gtkmm being a "better role-model" for C++ students, but your saying "you'll love gtkmm if you love C++" is the core of the problem, and the reason you still fail to understand why Qt is better. I don't love C++. I don't care about C++. I care about writing applications that do useful things. So I don't mind using a library which adds non standard keywords to C++, as long as it helps development. But you care for C++, so you can't do this. You care up to the point where you're oblivious of its flaws, and you don't realize that by trying to remain "faithful" to it, you make your life harder, not easier. Again, this is exactly how Gnome's C hackers happily handle the GTK+ Object System, not realizing that they could achieve the same things so much faster using C++ and Qt, and utterly convinced that what they do is "easy", because they love C and they don't need to learn another language.
Standards aren't sacred things. Theoretically you'll be better off following them, but in practice it's not always the case, simply because they were devised by fallible humans. And tools or languages shouldn't be loved, they should be used appropriately. Otherwise, when a better alternative comes around you'll ignore it, because you don't want to give up your own precious one.