I reckon QVC would have some way of censoring "live" chats, otherwise no guest would want to answer to the general public who might not even have bought whatever item and want to know why it's so expensive or whatever.
The censorship is, fundamentally, ignoring any tricky questions. It is an impossibility, ultimately, to answer every one asked. QVC would use this, if necessary, as an excuse for not replying to a question. Realistically, they could be telling the truth.