React: no <span> around text nodes - reactjs

Question

According to React 15.0 release notes, React is no longer supposed to emit <span> tags around text nodes. I tried that using jsbin and script
const Span = () => (<span>a</span>)
const text = 'text'
const Text = () => (<span>{text}</span>)
const Div = (<div>
<Span/><Span/><Span/><Text/>
</div>)
ReactDOM.render(Div, document.querySelector('#target'))
is rendered as
<div data-reactroot="">
<span>a</span>
<span>a</span>
<span>a</span>
<span>text</span>
</div>
So it doesn't work. I'd expect string a to be rendered without surrounding <span> tags. How is this feature supposed to work? Is it necessary to enable it in some way?

Answer 1

The feature is used when writing something like this:
<div>{'a'}{'b'}</div>
"a" and "b" was surrounded by tags and the dom was kinda full with this tags when using this multiple times in different components.
With 0.14.8 this was rendered as:
<div data-reactid=".0">
<span data-reactid=".0.0">a</span>
<span data-reactid=".0.1">b</span>
</div>
With 15.0 this is rendered as:
<div data-reactroot>
<!-- react-text: 2 -->a<!-- /react-text -->
<!-- react-text: 3 -->b<!-- /react-text -->
</div>
This is explained in https://github.com/facebook/react/pull/5753 and can be tested with something like https://codesandbox.io/s/N1znXxXL.