We should also use a fully-parenthesized prefix syntax so we don't get a mishmash of lines with and without parentheses used to override operator precedence!

I agree Javascript's "automatic semicolon insertion" is a terrible feature, but largely because the description is so hard to understand that programmers don't know when the semicolon is required.

In an expression-oriented language, like Xtend seems to be, the rule for when you need a semicolon is simple. The parser makes the longest legal expression it can, if that's not what you mean, then add a semicolon. It's no harder to understand than the lexer equivalent (the lexer makes the longest token you can, if you want to resolve the ambiguity insert a space), or the operator precedence rule (the parser will interpret infix operations using this precedence table, if that isn't what you mean use parentheses).

Matlab, for example, doesn't require commas to separate list elements, and doesn't require but allows semicolons at the end of lines, and nobody complains.