Only tangentially related (but hey, it's HN) - I'm so happy about the support/requirements for trailing commas in the modern language syntax:

    x = [
      123,
      456,
      789,
    ];

The oxford comma debate is so annoying because it clearly has nothing but advantages. Removing commas from a delimited list does nothing to resolve ambiguity, whether lexicographically or syntactically.

It's so useful as a delimiter and anti-ambiguity machine, that you don't even need spaces for it to work! See CSV or Japanese.

My very first programming language doesn't use commas:

  x: [
    123
    456
    789
  ]

I like this:

    x = [ 123
        , 456
        , 789
        ]