It seems to me that it affects mainly languages that don’t typically mix words from other languages. Japanese using English isn’t unusual, like Spanish. The German/English post and Italian/English mixed posts still error out when trying to translate.
I find this odd, since the forums use Google Translate, and if you are using Chrome, the browser has no issues translating any selected text. Here’s the screenshot of me translating the Italian post using Chrome’s Google Translate extension:
