Re: runnableExamples should generally be preferred to `.. code-block:: nim`

[Araq]

Yeah, well, `runnableExamples` is exactly what its name says, it's both, it's 
documentation that is **checked**. You dislike this conflation, but I like it 
(and hopefully others too) and I 've seen how Nim worked before we had them, it 
was worse. And to find out how well D's `unittest` works you can read on the D 
forum about them, they are not loved either. ;-)