They basically aren't doing anything.
We don't need such standards per se because neither of us is a lunatic but if I were in this very comment to make threats of horrific violence against you or your family you can be assured that hacker news tiny moderation team would waste little time in removing my ability to post because they give a fuck about the health of this community.
Facebook by contrast deals with a fraction of 1% of such issues.
For example telling people to bleach their autistic kids buttholes, that the vaccine contains a chip to track you or will kill you as part of a secret government plot, that covid isn't real, that you should prefer to treat covid with horse paste or take such as a preventative measure.
Hard cases make bad law.
Not only are some people unknowingly spreading such info but others are knowingly communicating such lies for the lols and for ad revenue.
When we enforce existing laws we take into account context and reasonable assertions of both judges and citizens to interpret situations and the law. The law books and case law is full of fuzzy situations we successfully litigate every day.
Yes, we do that now.
> Other lines can be carefully drawn.
I challenge you to draw a careful line for what is considered “harmful crap”. If you think you can do this, you are most likely a person who sees everything in black and white, and we don’t want people like that enforcing laws or policies.