I do not have any "Open" options on my right-click from "Show Source". From "Show Source" once I've highlighted the url, the only right-click options available are "Find Again", "Copy" (which I'm already doing, albeit from a keyboard shortcut), and "Select All".
If I try it from "Inspect Elements", I can expand the head tag, double-click to select the comment, click and drag to select the url, at which point my right-click only has the "Show DOM Properties" option available. But this has already taken longer than the above show source, then copy-paste, and go.
Turns out I was able to highlight and right click because I was selecting the <pre> embedded text in the comments of hacker news, rather than viewing source on the waterstones link.
I'm dismayed to report that the view source window doesn't give you this open. Even worse, if you right click on something that's highlighted as being a URL you can't even open it in a new window/tab. Colour me disappointed.
Actually you can just highlight the URL and right click, you get an option to open it in various ways... (firefox and chrome)