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It's an intended feature to increase immersion into the game. Duckish is the official tongue of Icarus.
Quack quack quackquackquack. Quack quack? Quaquaquaquack!
As far as I know the only things ducks say is "I am a male" or "I am a female", when they are young they say "I am a baby" but they grow out of that phase pretty quiack.
and some people believe are sensual.
It's the game's crappy codec, it's why you should always use your own Teamspeak channel even if the game has great voice chat support.