It was a splitter as stated in the Reply. Again, as stated in the reply I had the same problem and using the splitter helped bring down the high upstream and downstream values becuase of a poorly modulated line.
You are otherwise correct though, adding multiple splitters will degrate one's signal but one is not a problem. I added the one that I did to help stablize my ISP values and this significantly improved my lag. Once the ISP line is fully moduled to the correct values I will remove the splitter.
Again, though, I recommend this person look at the cable modem up/down power values and if they are not what they should be contact his ISP and requeat a line modulation further place a spitter on his cable modem in the mean time.