Back in the stone ages, I believe the Extropian list had extensive configurable collaborative filtering mechanisms. I didn't use them much, but that seems to me the actual solution. Let people trust who they want, and follow who they want. I see a Karma Score configured by me.

The failures of old mailing lists and Usenet were why social mediums universally abandoned killfiles and similar filtering mechanisms: the balance of costs was all wrong - a large number of people had to take affirmative action to ignore the small number of bad apples. It turned out to be better to actively curate the default than to thrust the burden of filtering signal from noise onto each and every user.

To give an Extropian-list-specific example: determined harassment was why Nick Szabo stopped posting there. The filters didn't help there.