There'd be nothing stopping that, certainly! But that's fine. It is a design challange in the hands of SN to make the process of "pasting a link" and having it auto-expand into a well formatted post, convenient enough. (assuming they decide to try—I would be interested in helping, I know reddit bots well, used to be one! ;))

I personally think many would elect to go the paying route though. I certainly would use it religiously, because redditors need saving man. They are desperate. Surrounded by insane orwellian "compassionate" discussion, always predictable and dishonest.