One of the particular values of Usenet was that everything in general was public; there was no need to log in (and especially no need to log into a particular group!) to read the posts on a given group, which was a major benefit for discoverability.

Similarly, the lack of any sort of authentication except at the point of ingress of a message into the system had many benefits for simplicity and lack of gatekeeping on new users, but it also meant that spoofing was readily possible.

I'd note that "client-based killfiles" are an emergent result of "UI is separate from the transmission system"; there is no basis for killfiles in the transmission medium. (There was, however, support for filtering on the server side with regards to accepting messages from other servers.)

Pre-post moderation was also somewhat of an emergent result -- my impression is that the only requirement in the system was that messages on certain groups needed to be signed with specific keys. The whole mechanism of "to post to this group, you send your message to a moderator who then approves and posts it for you" was largely outside the core system, and functionally there was no limit on what moderators could do to a post before posting it.