@scottjenson @mastodonmigration @stefan followers-only posts require the *victim* to report the attack. Depending on the volume and ferocity of the harassment, the victim may not be in a position to do this (either due to harassment across several channels, or unawareness of reporting and moderation options).
As an example, I piled into this thread to help out with an example, but I wouldn't have seen it to help out if it were "followers only".
I can see the positive value in being able to restrict a discussion, but it seems like "all my friends plus one more" might be a dangerous model.
Take all this with a grain of salt, as I haven't actually been subject to this kind of abuse, and am privileged in a bunch of ways which probably shield me from having to consider the worst of it.