A limited message width does not make sense for HTML or ELCode encoding since the text is laid out by the browser dynamically when displaying messages. For example have a look at this very message in your browser, and resize your window. You will see that the text flows dynamically, so the line breaks move with the window size. Furthermore the text entry uses a variable width font, so a fixed line length would not result in line breaks at the same vertical position. Therefore the message entry size scales automatically with the browser window. If you need lines with fixed length, you can only do that in plain encoding.