Exactly. I would never advise someone to use CoffeeScript without first knowing JavaScript, but I think very few people would do this anyways.
And even if they tried, aside from debugging issues, I think the article shows that it's pretty hard to work with CoffeeScript if you don't understand the underlying output code.
First of all why would you want to end up debugging on one language and writing on another?
This is why I specifically mentioned 'new developers'. But I also mean developers who know basic JavaScript and jump on the CoffeeScript hype wagon because its there and its hip.
And even if they tried, aside from debugging issues, I think the article shows that it's pretty hard to work with CoffeeScript if you don't understand the underlying output code.