Imagine that C on the PDP-11 had a slightly different syntax from C on x86, and the syntax were different from that on C on ARM, etc.
It's still a little irritating that they've changed things that CS handles quite elegantly to be less expressive, presumably just out of a desire to be different. I understand changes to the syntax are necessary for various reasons, but something like ! for argumentless function calls instead of () just seems like needless divergence. Was that extra character really killing you? Is the confusion with other meanings of ! really worth it?
About
The syntax of MoonScript has been heavily inspired
by syntax CoffeeScript.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 "--".
Edit: happily, an attribution has now been added at the bottom, as noted in child comments.