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

[Walter Bright]

On 8/2/2018 2:05 AM, rikki cattermole wrote:
> 8. if any identifier starts with a keyword and ends with at minimum one _, one _ 
> from the end of the identifier will be removed for mangling (but not e.g. lookup).

This will break existing code. A double underscore prefix is reserved for the 
implementation, which is why I went down that path.