My assumption about the board is correct, it shares the serial (USB) between the PC console and the RFID reader and therefor you will not be able to eliminate the garbage looking text
if you look closly on their site via your provided link, they have deliberatly dimmed out all the garbage to highlite the other text but it is still there and so even they acknowledge it is an issue (Expected behaviour)
the only easy way around this would be to use an LCD display or something on the I2C but or using other GPIO pins to seperate the Human communications from the RFID communications. based on what I am seeing you do here, i dont think that would be too much of a challange for you
