Nikolai Mavrenkov already created a good description of the problem on Stack Overflow: http://stackoverflow.com/questions/36893449/textarea-placeholder-isnt-shown-in-ie-11-being-rendered-using-react

I just can confirm it breaks in IE11, but works in IE10 (and other browsers) with React v15.0.2.

) {
        warning(
          false,
          'Textarea elements must be either controlled or uncontrolled ' +
          '(specify either the value prop, or the defaultValue prop, but not ' +
          'both). Decide between using a controlled or uncontrolled textarea ' +
          'and remove one of these props. More info: ' +
          'https://fb.me/react-controlled-components'
        );
        didWarnValDefaultVal = true;
      }
    }
    var value = props.value;
    var initialValue = value;
    
    if (value == null) {
      var defaultValue = props.defaultValue;
      
      var children = props.children;
      if (children != null) {
        if (__DEV__) {
          warning(
            false,
            'Use the `defaultValue` or `value` props instead of setting ' +
            'children on <textarea>.'
          );
        }
        invariant(
          defaultValue == null,
          'If you supply `defaultValue` on a <textarea>, do not pass children.'