What I’d really love would be a “BLOCK” button right next to “CONNECT”
When you hover over a profile pic, a white triangle becomes visible. When you click on it, it opens a menu that includes "block completely". Clicking on that adds someone to the superblock list. The app itself (like in the app menu, or the sidebar) is only needed to un-block someone from that list.
To block traffic from complete domains (servers), you have to go to the administration menu (I think it's the item "Security"), and there is a blacklist and a whitelist for whom you server will (not) federate with.