I think you missed the last part of my sentence. Usually, I don't add spaces inside square brackets. The only time I do is when the last element ends with a square bracket (be it #[] method of hash or another array definition):

    ["foo", "bar"]
    [ dom_class(record, prefix), options[:class] ]
    [ status, headers, [body] ]

This way two bracket sets are visually more distinct.
I just wanted to clarify that. Let me know if you don't agree and I will remove spaces.