I'm pretty sure it is! ( I'm also pretty sure that for a subset of the HN crowd, you may have just proven Linus's point :-P )

I think even HN readers must accept that the Windows kernel is rock solid. Maybe even better than Linux - Windows even gracefully handles graphics drivers crashing and can restart them virtually seamlessly. Linux just panics.

Graphics (speaking of modern 3D graphics) on Linux sucks, because NVidia and Co do not really care about it. It has gotten better (e.g. the deep learning crowd is mostly on Linux using cuda), but is still a far-cry from the stability of other sub-systems.

So I would say it is mostly gaming. There are not many games on Linux (again, getting better, but it takes time), so gfx vendors do not allocate big resources to support it, so the developer-experience is suboptimal, the classic chicken-egg problem.

The kernel is written entirely in C. See various WRK releases you can find online.

Until Windows 8, which they introduced C++ support on the kernel and deemed C89 as good enough, with the way forward being C++.

Yes, the latest VC++ do support C99 library, because it is required by the C++ standard and the new MSVCRT.dll is actually written in C++ with extern "C" entry points.