I do know that other lists I belong to do not repeatedly rewrite the same info over and over. I think that all depends on the e-mail software that the person is using to send the message. For example, in compuserve I have to highlight the text I want included in the next message before it is included in the reply.
Some software just includes all the text automatically, even the header.
If they have time, they will probably do it. All rights reserved.