Talking about Web View: In your settings, you can select which languages you want to see. This is a multi-select box! Recommendation: Select all languages you want to see, plus “Undetermined”! Do not select languages which you do not want to see. This will block posts and comments in unselected languages.

If you additionally want to block whole communities, you can do so at the same place where you can subscribe. The block button is hidden while subscribed.