Originally posted by ghelary I am aware of all this, rest assured.
But the link you provide isn't exactly applicable here. Because the Q isn't an APSC camera and a tiny sensor (in comparison) needs more careful consideration of diffraction effects -- whatever be the # of pixels.
E.g., the NEX 7 (despite its 24MP) has 3.9µm pixels while the Q has 1.55µm pixels.
And therefore let me tell you that a lens at f/8 is
not usable at the Q: The Airy disk radius at f/8 is 3.5 Q-pixels and everything above 2 pixels is mud (pixel-contrast with 2 pixel-radius Airy disks is 10% only and everything above is lost). Of course, you can use a lens at f/8 -- but don't expect sharp images then. OTOH, you're right, f/8 is still only 1.4 NEX7-pixels and it makes perfect sense to use a lens which is sharpest at f/8 on the NEX7 (although a lens best at f/5.6 would render quite a tad sharper).
Therefore and like the article you cite suggests, you'll need a lens which is sharpest between f/2.8 and f/4. Very few such lenses (for APSC and FF) exist.