Pushshift.io is pretty close to what you were talking about for Reddit comments; they make their archive available periodically at http://files.pushshift.io/red

Pushshift.io is pretty close to what you were talking about for Reddit comments; they make their archive available periodically at http://files.pushshift.io/reddit/ http://files.pushshift.io/reddit/ IIRC Pushshift is what powers sites like https://removeddit.com/ https://removeddit.com/ (to anyone reading this, please consider donating--this project is so cool)