Are you trying to use an emoji character? Something in your environment may not be set up to correctly process Unicode text. The byte sequence "F0 9F 98 9C" is the UTF8 encoding of the Unicode character for a face with stuck-out tongue and winking eye (e.g., it is an emoji character).
When I tried to use that emoji in this post, I got the same error. Removing it solved the problem.
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No love for Hamas, Hezbollah, Iranian Leadership, Islamic Jihad, other Islamic terrorist groups, OR their supporters and sympathizers.