I first attempted to format my messages in the Reply window, and they appeared in the Preview window exactly as I had formatted them, but after I posted them they had lost all the formatting. I asked at Zeev's board for help and fishweed pointed me to "/pre," which I have used now several times - to format text, not tables as you point out. In my opinion there should be better instructions and explanations given, and the format as it appears in the Preview window should be maintained when the message is posted.