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Hey #Trekkies (or #Trekkers)...
In Star Trek, why doesn't the Universal Translator translate people who are talking in their own language so that people don't know what they are saying?
This seems to happen a lot with Klingons when they want to insult humans, and there's always someone who says "I didn't know you spoke Klingon" or replies back in Klingon.
@Lorry A point I have often wondered about, ESPECIALLY with the Klingons.
I believe the answer is "because the writers needed it to for the story, and/or forgot."
@Lorry The Universal Translator can only translate by using English words that exactly match the lip movement of the alien words, and some Klingon words can’t be translated with perfect lip sync. Fortunately this isn’t a problem with any other alien languages. ;-)
@Lorry My head canon is that the universal translator has a swear filter.