Fully agree with you on the clunkiness of Google Groups. Thing is, most other mailing list web interfaces are even worse; not only are they lacking a threaded discussion view like we enjoy here on HN, they often only show one message at a time. And then there's web forum software like vBulletin. Don't even get me started...the pagination...the horror.
It's awful! And I agree with the other commenters that it used to be better. Usenet was better. A threaded mail client is better. HN is better. Reddit is better!
This got me thinking: why don't folks just deploy a reddit instance? It's open source, it's easy to hack, it works. I went ahead and did it myself. As a test, I wrote a little gateway program to import all the postings from that famous old Usenet dump [1], the one Google was so excited to preserve for us in clunky old Google Groups.
This Usenet-in-reddit experiment is surprisingly readable. Some of the formatting tricks and conventions from 30 years ago carried over without needing conversion. However, some things still need cleaning up before this is ready to be shown to the world.
If you're interested in helping out, it's a fun little project. Drop me a line!
[1] http://www.salon.com/2002/01/08/saving_usenet/