Domain blocking isn't quite the same as instance blocking. It generally works for text posts or image posts from that instance's users, but things like image posts may not be on the feddit.de domain. For instance, when I block that domain, I see the latest thread in m/ich_iel@feddit.de is actually from the domain discuss.tcncs.de (as shown in () next to the title). This is because the domain of an image post is where the image is hosted, as users posting images upload it to their own instance, not the instance the magazine is on. Ernest last said instance blocking should be coming in the future