If your user preference for language is set to "None (use default)" and you visit a page that doesn't have an "En/" or other language code at the begining of the URI, the page is served to you with German content. (the linked URL for example, which I get when I click on my username in the header).
The default language is set to English. This happens sometimes and I don't know why. I'll look into it.
This was fixed a long time ago.