No, by semantic information I mean information that's meaningful to humans but not to the JS engine. E.g.:

    // before prettier
    var matrix = [
        1, 0, 0,
        0, 1, 0,
        0, 0, 1,
    ]
    var result = (num % divisor) | bitmask
    
    // after
    var matrix = [1, 0, 0, 0, 1, 0, 0, 0, 1]
    var result = num % divisor | bitmask

No difference in actual behavior, but the linebreaks and extra parens were there to indicate the developer's intent, not to affect behavior.

Prettier's outlook is that this is intentional, and the developer should add "// prettier-ignore" comments to every line of code that has semantic information they want preserved.

I've never seen it be buggy, but it will often remove unnecessary parens. For example: (a * b) + (x * y) becomes a * b + x * y.

This the same code, but I often use parens for semantic grouping or to be 110% sure the operator precedence is correct for a particular formula. It's not a dealbreaker, but it does remove some of the meaning I was trying to imbue on the code.