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

[Atila Neves]

On Tuesday, 7 August 2018 at 02:25:32 UTC, Walter Bright wrote:
> Let's see if we can find some common ground.
>
> The boilerplate I suggested seems to enable DPP to generate 
> working code that behaves "as if" the namespace scope is not 
> there, even for nested namespaces.
>
> Is this correct?

Yes, I've already implemented it.

I'm not sure what the impact will be with nested namespaces in 
real headers. I guess we'll have to see.