Very nice and thank you! I recall a lot of topics in the past where folks were looking for an extension similar to one available on Discourse. This looks to be just that, well done!
A nice follow up, probably better suited for a different extension would be link tracking where each link click is basically tracked and display below the summary to show popular links shared in the discussion.
Personally I like it below the post, but perhaps it could be a user option whether to always display below the post, display below first post if there are less than X number of characters, or always display below discussion header.