I can completely understand wanting to differentiate from Reddit, but to me, this is a matter of convenience and priority. Putting right after the article implies commenting on the article is emphasized. Putting it at the bottom of the comment page implies a want to comment on the comments.
Maybe there’s a reason I’m not seeing here? Am I just dumb?
I like that part too. Makes you engage in the conversation already going and add your own comments to that, rather than repeating the same answer over and over.