I think a flaw in thinking is that users only see the one or two comments they make at a time -- so how bad could it be? A proper tracking service can and will pool all your data, from across a ton of websites, and can extrapolate a ton of data on top of that. And it's not even that hard, doesn't even take all that long. Consider this story by the Correspondent, highlighting just how little info they need (and that's from the point of view of someone hacking public wifi, let alone the fact that most websites willingly place these tracking mechanisms that probably get a lot more data!).