The devil you say!

I was taking a holiday at the seaside. Very lovely. Now I'm back.

This must be a troll thread. Our guest never came back to answer my question. I'm interested as to why he thinks the devil cares about quality, and "owns" the mediocre. Unless he's just saying he dislikes the mediocre and therefore they're "of the devil" so to speak. But maybe there is some old saying about the devil and the mediocre that I haven't heard?

Curiosity killed the cat. 9 times.

Alex