Observed this on react@16.0.0-beta.5

```js
import React from 'react';
import { renderToString } from 'react-dom/server';

const B = () => 'b';

console.log(renderToString(<div>{'a'}<B />{'c'}</div>));
```

This renders as `<div data-reactroot="">a<!-- -->bc</div>`. If you try to hydrate this you'll get the error: Text content did not match. Server: "bc" Client: "b".
defaultValue: undefined,
          value: props.value != null ? props.value : props.defaultValue,
          checked: props.checked != null ? props.checked : props.defaultChecked,
        },
      );
    } else if (tag === 'textarea') {
      if (__DEV__) {
        ReactControlledValuePropTypes.checkPropTypes(
          'textarea',
          props,
          () => '', 
        );
        if (
          props.value !== undefined &&
          props.defaultValue !== undefined &&
          !didWarnDefaultTextareaValue
        ) {
          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',
          );
          didWarnDefaultTextareaValue = true;
        }
      }
      var initialValue = props.value;
      if (initialValue == null) {