It would be possible for Reddit because Pushshift.io archives all the comments there and Reddit is still pretty small. I'd probably need to make things a lot faster. Doing it on a specific subreddit would be very feasible. I'll think about it but I don't actually know if I really want to do that because for instance I've been banned from subreddits before but I don't want a ban from when I was 12 years old to follow me around forever because my writing style hasn't changed. Moderation is the most obvious application of this kind of software.