Maybe that's an idea for a product: find discussions on HN, Twitter, Reddit, FB etc about your blog post and embed them on the blog where you would usually see the comments. Not sure how big the market is, but...
Maybe post your blog with something "unique[ish]"?
> I tried a few of those "commenting" solutions that attempted to pull the social channels into the blog itself, but they never seemed to recreate that 2005-2010 dynamic of active and engaging conversations occurring on a single post.
Probably, good enough for a Wordpress plugin.