Articles deserve their own page with their own comments
I agree with Abhishek Kasina and AJP for one main reason: it sounds like you're dealing with longer-form articles and not simple posts or tweets.
Facebook posts are more part of a bigger conversation focused on the user in general
On facebook, the posts a user makes are usually short and light on content, so allowing comments inline allows for a more conversational flow with the focus being on the person who's page they're posted on. The overall conversation is more to do with a particular person, not necessarily a particular post (i.e., all the comments together are interactions with the user).
Longer blog post articles are more specific with focused content
For a longer article, like a full blog post, the comments would be more highly specific to the individual article and not really have much relevance to the other articles on the site. Seeing all the comments inline would simply exacerbate the navigation usability for the user that wants to browse multiple articles.
Allow users to navigate and drill-down as needed
I'd say for longer articles, it would be best to provide a better list-view to give users a broader picture of the scope of the site's content (the lay of the land) to help them decide which article they'd like to spend more time with reading about and commenting on (maybe truncate the articles, provide an abstract, or simply list descriptive titles). Finding relevant content more efficiently will probably help engagement with comments more than anything else.
Conventional navigation helps me drill-down to what I want
My thought process when looking for stuff worth reading online is one of drilling down from abstract to specific, answering the following questions as I navigate:
Am I on the right site? Does this site have what I'm looking for? (fulfilled with site name, tagline, and homepage overview)
Are there any articles or other pieces of content that have been added recently I'm interested in reading about? (fulfilled with an index of available content/articles in abstract form)
Is the article I'm looking at right now worth reading? (fulfilled with descriptive titles and engaging first-paragraph or abstract)
Did I like the article I just read and do I want to participate in the ongoing conversation? (fulfilled with comments after I've read the article).
Articles warrant their own page and URL (with their own comments)
Comments for articles would make more sense to be packaged up in a special page to both contain the depth of the main body and house the conversation about the article in a container related to the content of that conversation (i.e., about the article, not the user/website). A unique URL also helps with sharing the article/conversation, further increases the chances of engagement.
And as an aside, I think that in general quality always trumps quantity.