My Moose Sense was tingling and I decided to check on the subs I moderate on Reddit. Sure enough, there were issues.
One of the three subs was set to 'restricted' (nobody can post or comment but the sub is still open), not private. (I'll pedantically put my explanation for this at the bottom so you can ignore it).
However, the seniorest mod, who is never around (seriously, his last post/comment was 10 years ago!), decided the sub should be private, not restricted. And he'd tried to do it himself, but because he hadn't been around for at least two years, the site wouldn't let him make the change! So I've changed it and it's now private.
Additionally, a report troll appeared, because he couldn't make any comments. I guess that's an even better reason to make it private.
[you can now ignore my exposition blather]
The sub was set to restricted instead of private because, well, part of this protest is also about people with vision impairments not being able to use the iOS mobile app and relying on 3rd party apps. If a subreddit is private, any message set by the moderators ("This sub is private because...") is not displayed by the Reddit mobile app. So the idea was, restrict access so any regular mobile reader would be sure to know what we were doing. But with 7000+ subs dark, I don't think it's any great mystery any more.