I want that as well, one of the German instances has a number of popular German communities, so I want to block them all (language barrier), but their users often comment in English elsewhere, which also gets blocked. I am using Connect, which lets you block by instance, but it's a bit over aggressive.

Yeah, that exploding heads nonsense could definitely disappear from my feed

Not in the api from Lemmy. Your instance admin would need to defederate