There are robust ways to do that. I've had discussions about it on Lemmy, so I could find the technical term again. The idea is to have everyone vote at the same time, and pass a turing test (for example a captcha) so it's much more difficult for a single person to vote many times.

But I had thought of a different possible solution for lemmy. There could be a top-level namespace shared by all instances. So there is only one global "antiwork" community. There can in fact be many with the same name but when you search for c/antiwork you will be redirected to whichever one has the most active users / month. Other communities with the same name can still be found through their URLs. But if there is a mass exodus from the global community to a different one, the new one will automatically take its place in the global namespace.

For the other problem of mods deleting things, tags will help. So you could have a setup where nothing can ever be deleted, only tagged as "deleted". Users have to turn on "deleted" in their filter and all the posts which were purged will become visible, along with all the spam etc which was rightly deleted.