. New posters getting moderated and delayed
There are 8 billion people, and millions of spam bots, on the internet. But focus for a moment just on the people. You are saying that anyone should be able to post anything, at any time, by signing up to the list and just typing $#&*&%$# or whatever. On lists.mailman3, some other lists being discussed are more general in nature, and they opt to implement spam filters, instead of moderation. Guess what... They are complaining about spam getting on their lists. Applying a first-time poster moderation, and then removing moderation, is appropriate for a small, expert, community. Other technical lists do that. If building an online forum aimed at a wider audience, with hundreds of topics, that's different, you wouldn't enforce the same types of moderation, it's application-specific.