Why should file names intended for executables be valid identifiers?

[Shriramana Sharma via Digitalmars-d-learn]

Adam D.  Ruppe wrote:

> It still has a module name that can be used in reflection, must
> be used in name disambiguation (at the linker level if nothing
> else, any functions are mangled with the module name so they
> don't conflict with C functions with the same name), and other
> things.

Sorry but I don't get this fully: can't a hyphen be part of such mangled 
names? Aren't they just strings that the linker hashes or something? (My 
knowledge of compiler/executable internals is limited.) And any reflection 
of the module name would also be just a string which need not be a valid 
identifier no?

-- 
Shriramana Sharma, Penguin #395953