Arduino Uno, weird characters sent to COM (SoftwareSerial)
The Arduino UART produces TTL level signals, that is 5V for high and 0V for low. A PC's RS232 port expects full RS232 voltages which can be -9V to +9V and are inverted.

Either use a TTL level serial adapter (such as those from FTDI) to interface to the PC. Or use a level converter like the MAX232.