Okay, for the benefit of a very few, I've set my tbird configuration to mailnews_send_plaintext_flowed = false;
Since I've got several accounts on this client and this is a *global* composition setting, I'm going to hope that it doesn't mess up composing on my other accounts. I've set the line width to 72 characters. If it does, I'm going back to flowed sent text and you can simply delete my messages when you see them. Of course, there's always the chance that this option won't work at all so If this makes you happy, fine. Otherwise, I'm not willing to do much else. --Chuck