Yeah, I share those same concerns. In fact, they consume a lot of my brainspace thinking about the project in the long term.

And, yeah, the coupling between Disqus (or whatever gets used in the long run) and DW would need to be as loos as possible. You don't want core site functionality to be dependent upon some other service which might or might not survive, or (maybe worse?) might or might not change its policies in ways which make using it undesirable.

I think I've got a decent set or architecture to handle that. I should work up a swim-lane diagram or something...