My intuition is that there are many 1000s of posters, but an absurdly high % of posts come from the top 200 posters (could like 35-40%). I also think that the top 50 posters could be responsible for something like 15% of all posts.
Posts by poster probably looks like this:
https://commons.wikimedia.org/wiki/File:Long_tail.svg
But...there are just too many posts. The masses are on here bringing in that massive long-tail of posts...many people with one or two posts a week.
Just my intuition.