If someone comes upon a posting in the middle of the
conversation, and wished to follow the conversation,
then he can go to his news server and review the history.

If the posting that he has come across whets his appetite,
then it is most likely to be the NEW contribution that is
responsible for the whetting, and the best place for
this new material is at the top.

If, however, it is the OLD material that whets his appetite,
then, by other practices that are vaunted as conventions, the
old material will have been much reduced by snipping, and the
someone will be motivated to go back to that older posting, and
so it will be irrelevant to him whether that old material is quoted
at the top or the bottom of the new posting.

"mike" wrote in message
news
Imagine someone coming into the middle of the conversation (posting
exchange) and not having already read the quoted part. With bottom posting
they (in particular me) can get up to speed on the thread easier.