“Public benefit corporation” is a meaningless designation. All it means is they have the option of putting their mission over their shareholders, not that they are obligated to do so.

I think you’d need a little more than that to make sure the restriction isn’t used defensively by harassers (one of the reasons people ask for this is to show others bad behavior in their replies). But it does feel like a solvable problem.

And Mastodon having more active moderation (since you can proactively look for an instance that meets your moderation expectations) also means the stuff that can’t be handled mechanically can be managed.