Looking at the more detailed breakdowns, it looks like there are a couple of servers (Lemmit.online, alien.top among others) with huge numbers of posts/comments that appear to be entirely bots. Are those counted in the stats? Could those be messing with the overall graphs? If Lemmit's quarter of a million posts a month are counted, its going to make the monthly posts stat useless when even .world only has about 15k posts a month.

Edit: Comparing the graphs to the server list, it looks like Lemmit is counted, so the main graph is likely misleading. I did look through some of the bigger servers, and their rate of posting seemed fairly linear, but there isn't a good way to check overall.