Fediverse

I do think it's important for a site to be willing and able to kick moderators who are abusive, especially in a major community. But as for a formal system for reclaiming a community, it would be up to in individual instance's staff.

There are struggles with a voting system in a pseudonymous environment like this site: how do you enforce identity? How can you detect if 5 accounts are actually just me and my sockpuppets? And how can you do that without making life horrible for people who want to stay private with tools like proxies and anti-trackers? It's possible to mitigate some of these problems but it's not an easy task once a community grows, and can involve compromise.

In a smaller site like this, raising complaints to the instance staff or on a /c/meta like community is a good first step and can be very effective if the case is strong.

In that case you can contact instance admins to remove the mod.

As a newbie, having some way for a community to democratically replace a moderator definitely sounds like it would be an improvement over most (all?) non-federated social media services, but I think there needs to be some kind of election framework for community leadership positions in general, and that would be how bad moderators get replaced. At the very least, I hope any voting would use the STAR method.