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

[Ola Fosheim Grøstad]

On Monday, 30 July 2018 at 03:05:44 UTC, Manu wrote:
> In 20 years, I've never seen 2 namespaces in the same file. And 
> if the C++
> code were like that, I'd break it into separate modules anyway, 
> because
> that's what every D programmer would expect.

It is common in C++ to have multiple hierarchical namespaces in 
the same file...