I would encourage every Fediverse software project to implement a “dead-man switch" on registrations: if nobody with moderator permissions has been active in the last week, then disable new account creation.
The Fediverse has a significant number of abandoned instances that are used by bad actors to create accounts and send spam.
We implemented this in Mastodon (https://github.com/mastodon/mastodon/pull/29318) and it has been highly effective.
Another consideration: new installations should not allow open registrations by default. This should be a setting that the administrator needs to opt into, and this is a good place to inform them that open registration instances require moderation resources.
In Mastodon, we display a warning when the admin chooses this option. Mastodon also support requiring moderator/admin approval for new sign ups, which helps a lot in preventing automated registrations.