I agree with this completely and wish that I had know to do it more aggressively, story as follows:
I moved into a new house that had marginal inside the walls wiring (or so I was told). No problem if you are a subscriber to HBO (and/or maybe CineMax and others...) you have CableGuard (just like the stuff you get from the phone company, LineBacker?). They are supposed to make it work with no cost to you....
It started with a separate new line from the "pedestal" for broadband, all good here.
HD channels were hit or miss at best, some worked some of the time, this was blamed on faulty equipment, fortunately it was their Moto 6412 PIII that was replaced, twice!
However after three trips with less intelligent "contractors" with the last one involving a "roof pen" (roof penetration) to run a new line from the pedestal that worked while they were there and did not work at night, I had to escalate, again. They finally sent a real Comcast employee out who did what should have been done the first call: Meter out the signal at the pedestal taking into account that HD signals are more demanding. He found a "bad splice" about 30 yards away in the submerged RG-2 that feeds my house. He fixed it, and ever since I have had NO HD problems, the 6412 still locks up for fun every couple of weeks, but that is a different thread. :-)
Bottom line, make them fix it, make them send a real Comcast person, one who gets paid no matter how long it takes as opposed to a contractor who is only thinking about how to get to the next job....
I did get several days worth of credit, that I had to call and request several times since they disappeared off my account after they were promised.