RS-232 format is:
1 Start bit
8 Data bits
1 parity bit
1 or 2 stop bits (usually 1)
So at most 12 bits, not 16.
The only thing I can think of that is framed 16 bits and would be emitted when a "key is pressed" would be Tribble's much beloved "Thonk" soud e.g. a digital audio output pin.
But a single 16 bit frame wouldn't carry much Thonk in it. But they may not have gotten around to making it work correctly yet.
