Is there any good reason why C++ namespaces are "closed" in D?

[tide]

On Friday, 3 August 2018 at 21:20:37 UTC, Walter Bright wrote:
> If we want to support interfacing with C++, we have to support 
> badly written C++, because that is the NORMAL case. Telling 
> them their code is **** and that they should rewrite it in 
> order to work with D is never, ever going to work.

On another note, why aren't const pointers to mutable data 
supported then? Anytime I need to write a wrapper for a function 
that has a parameter "T* const" I have to rewrite the C++ code 
cause there's no cross-platform way to mangle and call that 
function from D.

Does this mean you are for const pointers in D now or is trying 
to make D into C++ unreasonable now ?