> Bringing it into a private space like DMs is crucial, because it credibly shows that you're not trying to get brownie points from your in-group by bashing them in public.
The problem with DMs is that they are too much work for the passive onlooker.
Public forums like Twitter, Reddit, etc. should include the possibility of sending private signals: "uncool" badges that take no more than one click, but that are only seen by the original poster.
Perhaps a weighted surfacing of the "uncool" numbers. If a certain number of 'considered authentic' users mark it as such that starts to become visible on a post, and on the overall 'karma' of the author's profile.
The idea being if the author DOES care, and sees they're getting marked as 'uncool' then they have a chance to self-censor/edit/adapt. But if the authosr doesn't care then the audience still has a chance to see what some sort of 'curated' members have said about the content, and that the author's overall rating has potential to take a hit for it.
Any system can be gamed, of course, but the lack of clear options for contributing negatives about content is how we've gotten into this mess. Sole up/down votes are not enough.