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.

namespaceURI === DOMNamespaces.svg && parentTag === 'foreignobject') {
      namespaceURI = DOMNamespaces.html;
    }
    if (namespaceURI === DOMNamespaces.html) {
      if (this._tag === 'svg') {
        namespaceURI = DOMNamespaces.svg;
      } else if (this._tag === 'math') {
        namespaceURI = DOMNamespaces.mathml;
      }
    }
    this._namespaceURI = namespaceURI;
    if (__DEV__) {
      var parentInfo;
      if (hostParent != null) {
        parentInfo = hostParent._ancestorInfo;
      } else if (hostContainerInfo._tag) {
        parentInfo = hostContainerInfo._ancestorInfo;
      }
      if (parentInfo) {
        
        
        validateDOMNesting(this._tag, null, this, parentInfo);
      }
      this._ancestorInfo =
        validateDOMNesting.updatedAncestorInfo(parentInfo, this._tag, this);
    }
    var mountImage;
    var type = this._currentElement.type;
    if (transaction.useCreateElement) {
      var ownerDocument = hostContainerInfo._ownerDocument;