This serves a very simple purpose. When deleting a user in the Neos backend, ElectronicAddress instances are not cleaned up automatically, as there is an n:m relationship between Party and ElectronicAddress. For many use cases, such as the one we use in Sandstorm/UserManagement, we assume a 1:1 relationship between Party and ElectronicAddress. This command cleans up all "orphan" ElectronicAddress instances that are in the DB and have no relatiobship to any user.
To clean up all orphan ElectronicAddress instances, run:
./flow partycleaner:removeorphanaddresses
Example output:
Removing: foo@example.com
Successfully removed 1 orphan addresses.