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.

*/
  _createContentMarkup: function(transaction, props, context) {
    var ret = '';
    
    var innerHTML = props.dangerouslySetInnerHTML;
    if (innerHTML != null) {
      if (innerHTML.__html != null) {
        ret = innerHTML.__html;
      }
    } else {
      var contentToUse =
        CONTENT_TYPES[typeof props.children] ? props.children : null;
      var childrenToUse = contentToUse != null ? null : props.children;
      if (contentToUse != null) {
        
        ret = escapeTextContentForBrowser(contentToUse);
        if (__DEV__) {
          setAndValidateContentChildDev.call(this, contentToUse);
        }
      } else if (childrenToUse != null) {
        var mountImages = this.mountChildren(
          childrenToUse,
          transaction,
          context
        );
        ret = mountImages.join('');
      }
    }
    if (newlineEatingTags[this._tag] && ret.charAt(0) === '\n') {