Do not send messages on unrelated matters to the list. Before sending a question to the mailing list, check whether it was already asked by using the archives' searchable index. I'm supposed to read. I hate to admit it, but I've contemplated moving to Netscape to read my mail, just to get around this problem. I haven't got there yet, but it has crossed my mind.
Flat text forces the author the decide presentation, which is a big no-no in communication.