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.

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactDOMComponent
 */
'use strict';
var AutoFocusUtils = require('AutoFocusUtils');
var CSSPropertyOperations = require('CSSPropertyOperations');
var DOMLazyTree = require('DOMLazyTree');
var DOMNamespaces = require('DOMNamespaces');
var DOMProperty = require('DOMProperty');
var DOMPropertyOperations = require('DOMPropertyOperations');
var EventPluginHub = require('EventPluginHub');
var EventPluginRegistry = require('EventPluginRegistry');
var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
var ReactDOMComponentFlags = require('ReactDOMComponentFlags');
var ReactDOMComponentTree = require('ReactDOMComponentTree');
var ReactDOMInput = require('ReactDOMInput');