I guess that only works if by some chance instance b happened to catch EVERY post you made, which would require at least one person on b being subscribed to each community you ever posted in, right?
Yes, but if you use a popular instance, chances are high that they have every community you posted to
There is some significant amount of users here that fully / mostly abandoned social media and pretty often are in some kind of a post-reddit-lurker limbo, plus their age is around “I have a partner / family / job / hobbies / things in life I care more about than passionately posting / moderating online”.
Probably. I’m always surprised by the lack of activity on !parenting, but I guess most parents are probably busing actually parenting