How many of that 5 million are actually active users, though. I don't mean power users. I mean users that post/comment with some frequency greater than "rarely"

How many of that 5 million are actually active users, though. I don't mean power users. I mean users that post/comment with some frequency greater than "rarely" and browse regularly. I'd bet the vast majority are users who come in to ask a single question or make a comment in one thread that caught their attention, and then never engage with the subreddit again.