You can try inline comments at medium.com or quip. They are good for some things - like feedback on particular aspects of an article. They don't seem to stem active discussions, though. A mix is possible, though. Quip, for example, does inline comments and a sidebar with both inline and direct comments mixed into one feed.
and in medium.com one feature that leave note on pic ..for author or to other ppl with @ option..that is also good..
we should have this feature..with nested comment..if possible..in trident post module..
i think it will get more popular in future..