for users of thunderbird, up to 17.0.9 anyway, when you compose a reply to post that has long lines, over 72 characters, pressing
will form line breaks and quotes in reply.
that is if you have;
edit > preferences > advanced > general > config editor
mailnews.wraplength default integer 72
doing such makes for easier reading of post as it makes post more clear as to where quotes end and replies begin.