> newly joined users post a disproportionate amount on the website.
What is your definition of a new user?
> For me the answer, as borne our in data, is no. I find from ~ 2016 a change in the types of discussions on the site and find that the newer the poster distribution skews from that time period onward the less interesting the discussion becomes to me.
I am curious: Can you elaborate on how such analysis is being made?
A poster that joined in the last 2-3 years.
> I am curious: Can you elaborate on how such analysis is being made?
Try doing analysis on the time at which posters in a thread joined this site. I weigh their dates based on the number of times they comment in a thread. If you do that you'll see a recency bias. The mass of the distribution is clumped more heavily in the last 3 years since the article's submission. If you think about it, that makes a lot of sense. People are probably much more energized to comment when they first join and eventually get bored and stop. You point out a really similar effect out in your own analysis about posters that stop posting after a year.