I ended up messaging the admins at the 16 instances show in the attached image. I pointed out their wild user numbers, and referenced the lemmy.ninja post detailing how that instance scrubbed suspicious accounts from their user database.
6 admins responded. They had all noticed the odd accounts and either thought the numbers were wrong, or weren't sure how to purge the suspicious accounts without nuking their databases. In the end they managed to delete a combined total of about 338k dormant accounts from their instances. (One of the instances seems to have gone down since then.)
I never received a reply from the other 10 instance admins, though 8 of those 10 instances appear to be down (as of 27 July 2023). 2 instances are still up and unchanged.
Between the actively removed accounts and the downed instances, this represents a loss of 930,004 inactive Lemmy accounts!
You can see the drop in the graphs on The Federation. The total number of Lemmy accounts has been cut in half over the past 3 weeks, from a peak of 2.18M to today's 1.09M. The change is mostly from these 16 instances.
I have to admit, I did not expect such a large change when I started this! Hopefully this bodes well for Lemmy's future as a place where actual humans interact, rather than a cesspool of automated comments and upvote/downvote brigading.
That's all I have for now. Keep your stick on the ice; we're all in this together.
How did those accounts get created in the 1st place? Arent there captchas? Or are there ways around that? Strong captcha system should he implemented in lemmy by default
Captchas are a low bar to modern standards. All the advancements in AI are a problem for captchas. Machine vision tools have become abundant and simple. Unfortunately, I'm not sure what more you can do except require human review of access.
I'm not sure about all of them, but at least some of these instances did not have captcha or email verification enabled when they were first set up. They were easy targets for scripted account creation