Agreed on points in the article. Would be good to note that using thinner stroke for interior details (and thicker strokes for "important" lines that represent large depth discontinuities) is also a reasonable design choice (example: https://dribbble.com/shots/1324699-Icons https://dribbble.com/shots/1329630-More-Icons )–this is pretty common in non-icon illustrations as well.
Don't really see a point in all the gifs. Would be much easier to see the difference if you just showed two separate images of good/bad examples.
Those gifs are awful and distracting.
Good guidance badly executed. Click to reveal with no sideways scroll might have been better
The persistent webpage bar takes up 1/3rd of my screen on landscape. Highly irritatng
Those GIFS are highly annoying and not useful at all.
Questionable UX and site design choices by the author aside, I found the advice for graphic design of flat icons to be spot-on.
Re-packaged into a gist or some other less-annoying format sans-gifs, and this would be a stellar resource.