I feel like it would be useful to be able to filter toots by language in the local/federated timelines. As an English speaker, I don't really want to see toots in other languages.
It seems like other platforms get this for free simply because you probably don't connect with people who speak languages you don't.
The obvious problem being that it's not always easy to programmatically classify languages (see any automatic translation suggestion tool).
I suppose it's just on me to scroll down.