Nope.  It was, AFAIK, totally decentralized.  You posted your post to the news server your reader was connected to, who then propagated it in a P2P network of news servers.  You could run your own news server of course but only institutions did so, because that was "heavy" at that time for the existing technology in those days.  In fact, it would even be "heavy" today too.  Bitcoin's block chain is ridiculously small compared to the news groups' daily volume.  That said, a news server mostly didn't keep old stuff.  One month of history was usually standard.  If you wanted to keep stuff, it was entirely your business.

The "consensus" was simply everything, because there was no specific order needed, there was no contradiction to be resolved etc...
Of course, every news server could decide for himself whether he propagated the article or not, but the standard policy was to propagate everything.  There was no crypto needed for that.  You didn't need an "account".   Everyone could just post and put the "credentials" he liked - but of course, nobody would stop you from signing your messages.

The exception were moderated groups.  They only accepted articles from a specific e-mail address, the moderator's e-mail, and if you "posted" there, in fact, you sent an e-mail to the moderator, who could relay it to the news group or not.

https://internetworkingsecuritysafety.blogspot.fr/2017/03/what-newsgroups-are-and-how-they-work.html


Of course this could have been improved.  In fact, Adam Black's hashcash against spam would have been a solution for high-volume mass posting.  But that was not the real difficulty.  The real difficulty was not the "standard spam", but rather the "annoying posters", and that is something you cannot solve without human moderation.  So in the end, for some serious discussions, people just went to moderated discussion groups, which were the inspiration for internet discussion forum software.

Slight improvements of usenet would have implemented the features you are longing for, like multiple versions of moderated groups with different moderators, but visibly there was not enough demand for that.  In fact, technically, the system was already possible: instead of having one moderated group, you could have as many versions of it as you'd like, with different moderator e-mail addresses: every moderator would decide, independently, what posts to relay, and have his "fan moderated group".
But of course, as I said, nothing stops one from having an overlay on an un-moderated group, where you have your news reader load Joe's moderation preferences from Joe's web site, who has published the message ID he thinks should be read, and your news reader only showing those that have a corresponding message ID on Joe's page.  You could even make logical combinations:
"I want to see the messages that are approved by at least 3 of the 5 guys in the list Joe, Jack, James, Jeffrey and Joey, and are disapproved by at least one of the 3 girls Mary, Jane, Helena" or other fancy things.

I only wanted to point out that decentralized discussion platforms existed in the 80-90-ies and essentially disappeared, which indicates the relatively low value people attach to this decentralized paradigm.  Maybe it could be revived, but it doesn't need much sophistication to do what you want.  No need for much crypto/block chain/consensus/.... KISS.