Indeed. It also saddens me that it does not stick to CS conventions - lots of extra cruft ( the ! for zero-arity method invocation -- instead # for comments etc )
Language using "--" for comments include Lua and Haskell.
You've made me curious - what languages to you use/know that make you think "#" is a "CS convention" for comments?
EDIT: Found a reference:
http://en.wikipedia.org/wiki/Comparison_of_programming_langu...
Further edit: In response to the clarification that CS meant CoffeeScript and not Computer Science (nor the riot control gas), the point, I guess, then follows other commentators, who observe that Lua, to which this compiles, uses "--".