While we're playing a friendly game of "quote Robert Cartaino"...
We also have several "language learning" sites which allow a full-immersion experience by posting questions in both English and the target language of that site.
Robert Cartaino, 2019
In the context of a feature request for bilingual tags he wrote:
Despite its outward appearance, Esperanto SE is still an English-language site whose subject just happens to be learning another language. Yes, there is a strong component of full-immersion learning, encouraging reading and writing in the target language — and we fully support that — but purporting to support non-English communities in this one feature ONLY presents a problem our international design was meant to avoid.
Robert Cartaino, 2019
(This is also relevant for What's a suitable Chinese name for the Community bot?)
The Russian Stack Exchange (in Russian) arose atypically:
The Russian Language [in Russian] site was imported from another community at the same time that Stack Overflow in Russian was imported. The sites were seeded from HashCode because they already had a good base of Russian programmers.
animuson, 2017
There's also the matter of Hot Network Questions:
International Stack Overflow sites are now excluded from the Hot Network Questions list entirely.
Adam Lear, 2019