Did I just have a very different Reddit experience to everyone else or is this a massive circle jerk?

Fair, I never went on those subs and I'd imagine most Redditors didn't. I'd also imagine there are some Lemmy instances which are just as bad if not worse. I guess that's a bit different because federation means those communities are isolated from other instances, but I don't know if practically it's any different when it's so easy to have accounts across multiple instances. I'd imagine anyone using one of those highly isolated instances on Lemmy will have an account on another instance.

4.6 million subscribers all time out of 1.7 billion monthly active users. Roughly the 90th most popular subreddit, which is quite large but it's still a fraction of a percent of users.

Was the issue introduced with the latest version of jerboa?

Except there's no way for consumers to select based on climate impact at the moment. We can't see the carbon footprint of the products we buy on the shelf and there's no market mechanism rewarding companies providing products that have a low carbon footprint. We either need much heavier taxes on fossil fuels at the original point of sale, or mandated carbon footprints on product labels.