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

[Walter Bright]

On 7/30/2018 2:12 PM, Manu wrote:
> We're all happy with the D
> module system, that's how we want to organise our code. Please let us
> organise our code using the D module system.

I have literally no idea what you mean. That's why I suggest you show what your 
C++ code looks like, and what you want to do with modules in D.