The trouble was, I had to hire translators. They weren't programmers, so the translations were (so I've been told) peculiar. When I'd modify the compiler, trying to keep the translated text in sync was a nightmare.
The last straw was when I found out that essentially none of our customers used the messages in their native language. They preferred the English versions.
So I just gave up on that with D. (Although the D language itself has excellent Unicode support, the user interface is all in English.)
Some members of the D community have taken the initiative to create documentation in their native languages, which is great.