Four million threads? So that would mean a billion posts if the average thread had 250 replies.
(I don’t imagine the average is that high, maybe 80 for a total of 320 million, about one post for every legal resident of the U.S.A. )
Or was it really just four million posts?
24 years is 8,766 days so that would imply an average of 455 threads per day over the approximate life span of FR.
Having followed both popular and obscure topics for 15 years, I would guess only about 30 to 60 comments per post. Of cours there are those that get thousands, but they are a relatively small percent. Try entering random topics in the search bar and see how many posts get only a few dozen comments.