I think the difference between syntax and semantics can be quite blurred sometimes. For example, CoffeeScript embraces the "everything is an expression" philosophy and that's a pretty big difference for me compared to plain JS; it affects the way i write -and think about- code in a much deeper way than using indentation instead of braces. So, is the difference between having statements and expressions as different constructs and having only expressions just a syntactic difference?

Another aspect in which CS differs from JS is that it provides built-in classes; which i think can make code written in CS much more consistent compared to JS, where everyone seems to like inventing their own way of writing classes.

And i'm sure i'm forgetting other aspects in which CS differs from JS that i wouldn't consider "just syntactic".