I have always had the impression that the change of name feature of this forum was merely for fun and nothing serious without knowing that the intention was related to privacy. My thinking was based on the points I have given above. If there are ways of hiding the history and previous activities of individuals when they change their names, then we can attach the world privacy to such exercise.
As theymos mentioned in his post, whatever you post online could be archived very quickly. When it comes to Bitcointalk, at least two known services archive your post within a second. When someone changes their username, their account still contains their posts. Not only that, they are still on the trust list of people, and the feedback they received and given remains the same. So, a name change doesn't change much, it's just a name change and that's it. Otherwise, I have created my account with my real name and I would have asked for a name change as well. But I am not doing that because I don't think a name change will affect me much.