I would never need to write in more than one language in the same message.

Bon Appetite! Wait, are those quesadillas of surimi?

Ok, this was an exaggerated example using French, English, Spanish and Japanese (although most people would consider the message as English only due to the fact that the words/concepts don't exist in English).

But being honest I find myself often writing messages that combine words of different languages because the words/concepts doesn't exist in the language I'm writing.

In the past I didn't even had to think about it, because I simply wrote what I wanted to write, but the fact that I'm forced to struggle with text prediction has made me put more attention in those details.

I often use english words in Japanese messages I write, and writing roman characters in the Japanese interface is a miserable experience. I'm toggling back and forth pretty often.