We wrote a post about why we decided to go English only on Fosstodon. If you're interested in a long-form explaination as to why we did it, check out this post:
@fosstodon what about allowing bilingual posts, where the content is in English and then repeated in another language? That might be a good compromise.
@peterhebert that's what we're discussing currently as a viable compromise for people.
Fosstodon is a Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.