It's the fact that the "URL" starts with a !, so it gets the formatting of an API Command Button instead of a link. I'm not sure what formatting rules Ability Command buttons ("URL" starts with ~) get. An actual URL that starts with http:// or https:// will get formatted as plain text, unless it ends in .png, .jpg, or .gif (mostly sure on that last one) in which case it will be formatted as an image.