I was facing a similar issue. It turns out that, in my case, was highlighthjs removing comments from the generated dom.
For text, React 15 is adding comment with the reactid instead of a span tag, as in:
<!-- react-text: 248-->
Another Search
<!--/react-test-->
Can you try something like this?
<Link className="dark button" to="https://stackoverflow.com/"><span>Another Search</span></Link>
This will force the generated DOM to include the span with the proper data-reactid attribute.
I would file an issue with react-router, maybe they can do that internally so you would not have to bother about it. But there are challenges with that as the Link child could be basically anything.