On version 0.19 you can block instances so that you don’t see any posts from that instance, instead of having to block communities one by one, you still see comments from users of that instance in other posts so it isn’t completely blocking the instance.
I mean, comments have languages and you can filter but the automatic detection isn’t very good.
The ability to mark communities as being a certain language by default (applying to all posts and comments unless specified or detected otherwise) would be great though.