The only reason you can't do this in C9 is because the forum editor is doing some validation on URLs and strips it out. You can work around this with a URL shortener.
However, with a URL shortener, the redirect works, but you get a "The webpage cannot be displayed" message. The URL, however, is still displayed in the address bar, so you can click refresh. Then it works.
Note: TinyURL is one of the few services that doesn't do URL validation.
You'll see that a direct link from HTML does work. Go to this preview page, and click the "Proceed to this site link".
Note: Obviously, this works only in IE10 and above. Other browsers have no idea what the hell the "ms-windows-store:" protocol is.