I admit that I talk to it in English the most (as it's my native tongue) but I had read here that it has gotten noticeably worse in other languages, even making grammar mistakes in linguistically-close-to-english-and-sufficently-present-in-training-data western european languages like German or French.

I do enjoy translating things into Sindarian or other conglangs from literature though.

I had a theory that giving it the custom instructions in latin might give better results, but i haven't had time to figure out how to benchmark something that's so non-deterministic and black-boxy