Gregory's Server
Okay, I tested.
I am sorry. You are correct. This feature is only for your "notification", so it is incomplete and won't actually be effective in helping with the harrassment problems.
I'll see if @renchap can take another look at the open issue on GitHub.
Notification isn't the problem. The option should be to Mute and/or Block.
It might be that mute and block lists are actual lists, rather than what notifications are, which is more like a stream. So maybe there will need to be some automation running server side to do it. There will need to be some safeguards to keep the lists from growing too big too fast.