It may be useful if you want to do something more creative than just subscribing or unsubscribing to a list. All lists are maintained by Majordomo. Some lists are closed. All lists are unmoderated, but closed to non-subscribers. This is to reduce the amount of spamming.
Header rewriting NO header rewriting is done on submissions.
Archiving In general, all lists are archived. This may change. In general, people are removed from a list after three consecutive bounces to the list maintainer, whenever the maintainer feels like it. If their system is so dumb as to send bounces to the message sender , they are removed at once and without warning. This system is in the constant process of being modified, as most things computerish.