...this place, more than anywhere else, people duplicate the information that precedes them in a thread. It is nothing to see almost an exact re-statement of an idea several times in one thread -- none of them acknowledging the previous.

Where I've seen that, its been in response to people arging the same point over and over and NOT responding to the information of previous posts. I think it used to happen to one particular person because he had a habit of "skimming" other people's posts. But then, you could be talking about a completely different situation.