> Code Review should be about catching mistakes.

Overly-complicated code is a mistake. Maintainability matters almost as much as a passing unit test. You want your code reviews to catch meaningful things, but they often end up being about things like this (fixing inefficient small bits of code).

e.g.

     function isDry(weather) {
         if (typesUtil.isSunny(weather) ||
             (!typesUtil.isSunny(weather) && typeof weather.hasSnow === 'boolean' && !weather.hasSnow)) {
            return true;
        }
        return false;
    }

vs

    function isDry(weather) {
        return typesUtil.isSunny(weather) || 
        (typeof weather.hasSnow == ‘boolean’ && !weather.hasSnow);
    }

vs

    function isDry(weather)
        var hasSnow = false;
        if(typeof weather.hasSnow === 'boolean') {
            hasSnow = weather.hasSnow;
        }
        return (typesUtil.isSunny(weather) || !hasSnow);
    }