As I was looking through our content, I found we have a new exercise on comparing decimals! It was written just 10 days ago (and hasn't yet been added to the main site):
With questions like 0.3 __ 0.03 and 0.02 __ 0.1, I think you'll find that the exercise touches on exactly the misconceptions that you've seen. In addition, the hints use area models to explain the comparison, just as you suggest in your post.
Minor bug report, hints 3 and 5 (where the values are displayed as hundreths) overlap with the previous hints (where they are shown as combinations of tenths and hundredsths) for me on Firefox/Ubuntu, but look fine on Chromium/Ubuntu.
As I was looking through our content, I found we have a new exercise on comparing decimals! It was written just 10 days ago (and hasn't yet been added to the main site):
http://sandcastle.khanacademy.org/media/castles/Khan:master/...
With questions like 0.3 __ 0.03 and 0.02 __ 0.1, I think you'll find that the exercise touches on exactly the misconceptions that you've seen. In addition, the hints use area models to explain the comparison, just as you suggest in your post.