Tbh, and I plan to do this for piefed.social soon (and rimu has given me the go-ahead) - abandoned discarded communities with literally zero posts need to be purged by instances. It’s just clutter.

Cool, but there are other instances.

Then there is the issue of communities with a decent number of subs (much more than active communities) but where the last post was 7 months ago and they have 0 MAUs. While a community with a lot less subs can have several posts per week and at least some MAUs (couple of hundred).