Provide an active user count which is not dominated by new registrations

[nemobis]

Pitch

When reporting on the activity in the fediverse and Mastodon, people are often confused by the fact that the MAU figure is inflated in periods of higher than usual new registrations, even if user retention is stable or declining. It would be useful to have a figure which only includes the "really" active users, without the users who register and login one day never to return, so that it would jump up and down a bit less.

A couple possibilities for new statistics/stats could be:

• add a count for active posters (similar to active editors in Wikimedia or active users in MediaWiki), for example having performed at least 5 actions of any kind (post, favourite, bookmark) in the past month;
• add a count which is still focused on logins but doesn't count users registered in the previous 30 days (it could be called "returning active users").

Motivation

As previously discussed, the "active users" or MAU figure is actually just a count of users who authenticated in the past month:

• Definition of active users #18920
• Mastodon Reports monthly logins, not monthly active users #24528
• Active user counts should not count banned users #18861

Some examples from fediverse.observer for mastodon.social (where in July the MAU went up by about 60k including 100k new registrations) and toot.community (where the influx of 30k new users produced about 5k active users, but the MAU was well above that figure as long as new users kept coming):

[nemobis]

The active user ratio from https://the-federation.info/platform/21 is another way to spot some oddities.