The spec isn’t so interesting as what is needed to implement it efficiently. Maybe less of a challenge today since usenet is out of vogue. I knew someone who ran a Usenet service in the heyday and they spent a lot of time working around hotspots and limitations in storage capacity and I/O throughput. They typically had clients and servers accessing the same servers and it could get overwhelming during peak hours. I think all of these things are solved problems today, if someone was implementing an nntp server from scratch today I expect the backend would look very different - probably a lot more separation of content and metadata, a lot more caching between front end clients and the backends. Having SSDs instead of spinning disks would make a huge difference.