How (racist/sexist/whatever) harassment on Mastodon works:

1. Harasser replies to their target's post, with the reply set to "followers only", saying the most vile stuff you can imagine.

2. All the harasser's followers join in on the harassment, posting more vile stuff.

3. Nobody but the target and the harassment crew can see the vile stuff that was said.

4. Target is traumatized. Nobody else can see why.

5. Everybody says "I don't see it so it's not happening."

https://community.hachyderm.io/blog/2024/08/12/hachyderms-introduction-to-mastodon-moderation-part-1/

Hachyderm's Introduction to Mastodon Moderation: Part 1

The first post in a series about Mastodon moderation tooling. This post focuses on context for the upcoming posts.

Hachyderm Community
@dave

But Dave, couldn't Mastodon just not allow you to reply followers only to a public post?

Dave: "Sure it could, but the harassers would simply run a system on their instance that doesn't have that restriction. The Fediverse is more than just Mastodon. And Mastodon is open source so they could also still use Mastodon but remove that restriction."

@MxAlba @dave No, it doesn't work like that.

If their instance was breaking the reply restrictions rule, your instance would detect that when they try to federate the reply to your instance, and would reject it. Then you would not see it, and it also would not get federated to anyone who opens your post looking for the replies.

Your instance could also use detection of this behavior to automatically place the offending instance on limited federation and add it to a review queue of abusive instances that are candidates for defederation.

@dalias @dave

Thanks for the education! So it does sound like that might be a solution...
@MxAlba @dalias @dave That would be enormously disruptive. I have followers who only post followers-only. They would not be able to reply to my public posts unless I also followed them. Several hundred more people follow me than I follow. I can't and shouldn't have to follow them all.
@Rhube @MxAlba @dave I think you misread because the above has no impact on public posts without any reply restrictions. It would be part of the long requested reply control features one could use if you want to limit who can reply to you. And one very useful limitiation would be "you can't change the scope of who the post is visible to".
@dalias @Rhube @dave

Of course that also would technically block people from privately responding to a public message...
@MxAlba @Rhube @dave Only if the public message has a reply control preventing that. In which case if you really want to reference it in a DM you can just include a link or quote (if quoting permission allows that).