[krapp]

>Usenet even allows noting threads, blacklisting users, etc. But not controlled by any single company...

Because it relied on third party clients, which have more or less been replaced by everything being done in the browser and the closed black box that is a "website".

Although I suppose you could still do that with a site which provides an API, or some kind of official set of browser plugins but the experience probably wouldn't be the same.