Hi nusenu. David is listed as the maintainer of bad-relays@ [1] so this is a question for him. Generally speaking the choice is simply: should all new senders go to a moderation queue or not. Advantage of moderation is no spam, but disadvantage is more work for David. We have very few moderated lists for this reason. It works for tor-project@ because Roger, Moritz, and I stay on top of it but if you don't have moderators looking at the queue almost daily doing so will be painful.
Cheers! -Damian
[1] https://trac.torproject.org/projects/tor/wiki/doc/emailLists#AdministrativeL...