If you call Google cache "tracking what you post", perhaps, but they have no way of determining who is who unless you specifically give that information out. In addition, this is a public forum, and as such there is no reasonable expectation of privacy of what you say, just of who you are (anonymity of person, not of content).
In contrast, tracking browsing traffic at the ISP level makes it ridiculously easy for Charter to say that specific person xxx goes to sites yyy, making it trivial for the ISP to know who is looking at what (and, of course, to sell that information).