[XeTeX] why does Latin Modern Mono have some stretch and shrink with XeTeX ?

[jfbu]

> 
> Three related issues were filed in the fontspec bug tracker, one of which
> has been closed:
> 
>   https://github.com/wspr/fontspec/issues/97
>   https://github.com/wspr/fontspec/issues/98
>   https://github.com/wspr/fontspec/issues/99
> 

Thanks,
Jean-François