Why does chrome keep showing a "Translate this" button on pages (i'm on signup page). There is something which is making it think it is not in English. Just a heads-up!
Raindrop outsources some of their development to Ukraine. Perhaps, someone left `<html lang="ru">` somewhere. Many IDEs and editors use system language inside their HTML templates by default. I think, WebStorm does it, maybe some others.
In addition, many companies like Facebook offer localized versions of SDK downloads and Widget scripts. Thus, when a developer somewhere in China downloads the SDK and puts the <script> tags on their page, people from all over the world will see Facebook authentication dialog in Chinese.