As a node developer, seeing
any official, open source package in CoffeeScript is a red flag.
The sibling I made a link to a thread about CS in Atom. The creator of express.js has his take:
"Hell I had to rewrite a coffeescript driver this week because I can't have our company relying on things written by people who are unfamiliar with javascript, throwing strings, super awkward apis, lots of indirection, and stepping through the compiled source is a nightmare. It's not like I didn't want to contribute, I even tried for a while, but it's just not worth the hell, it was quicker to just rewrite the thing. Not to say all coffeescript libraries are written poorly, but regardless you're really not gaining much, just losing a lot." [1]
If you write an open source application in CoffeeScript, you're not doing the community a favor, you're doing yourself a favor. They pay the penalty.
[1] https://discuss.atom.io/t/why-coffeescript/131/8