Perhaps that is what they already had. If they were to use your app, they'd still have to manage and carry the costs associated. That probably isn't their main motivation.

I remember a few years ago whenever you clicked on a Guardian news link in Facebook it would try and get you to sign up to their Facebook app/plugin, that would then publish on your timeline what you'd been reading, let alone commenting on. I thought that was a bit ghastly.

I'm assuming that when you make a comment through Facebook on the Huff post, it displays on your timeline or some such, providing additional reach for the story.