Why foreach(c; someString) must yield dchar

[Kagamin]

Jonathan M Davis Wrote:

> Not to mention, the Linux I/O stuff uses UTF-8, and 
> the Windows I/O stuff uses UTF-16, so dstring is less efficient for dealing with 
> I/O.

If we take dil as an example of application doing much of string processing. How much string processing it does and how intensively it communicates with OS (with string transcoding)?