Not sure I agree on the harassment issue. The protocol layer is dedicated to providing a stable foundation where anyone can post anything, and I don't see the issue of harassment changing that, because whether a note or reply is harassment is a value judgement. It might not be the intention, and there's a spectrum that needs to be considered. The protocol layer can't really deal with that level of complexity. I think the functionality that you are looking for is in network logistics, where we could be given the option of seeing whether an npub is a close connection with someone else that we have already muted, and make it an easy single click to mute that npub as well.  That would work well at the client level, if the client has the type of network analytics that I'm thinking about.  That kind of development work is going to be coming, but right now I haven't seen anything.
And I think the second issue of "random jerks" is also going to be related to network analytics as well. We can see a list of Nostr Highlights in our feed.  Maybe a client could dig a bit and provide a list of "most muted npubs". If someone decides to be a complete jerk to anyone and everyone, they can post whatever they want as long as they are in a silo that protects the rest of the network from abuse. So put them on a list and give people the option to mute jerks sight unseen.