Very interesting. Will this cover all subreddits, or all above a certain size?
I've switched fully off of reddit in protest, and have turned to HN and Lemmy as imperfect replacements. The main remaining thing I've noticed reddit excels at is researching things like product recommendations.
Searching a keyword on BIFL, along with poking through various threads on whatever niche community might exist for the topic, has been one of the most reliable and useful ways to get a sense for what brands or models are best when considering a purchase.
So far Lemmy is not close to replacing this so it would be compelling if your project could change that.