In the Sefer B’Tuv Yerushalayim it relates that the Maharil Diskin refused to speak to a certain Talmid Chacham of Jerusalem because he used to spek only Loshon HaKodesh. Said the Maharil Diskin, “For generations we are accustomed to speaking Yiddish, not Loshon HaKodesh.”
p.s. However it seems that R’ Sonnenfeld later regretted this position.He even answered the Mandate language replying he spoke hebrew