The text editor now has the capability to change the cols attribute in the pre tag, but the change doesn't show up because changing cols doesn't cause a reflow. It should. The mail compose editor will need this. To test this, run the editor on EditorInitPagePlain.html (unfortunately this currently requires editing chrome/editor/composer/content/default/EditorAppShell.xul and changing EditorInitPage.html to EditorInitPagePlain.html; hopefully we'll have an easier way soon, and eventually the mail compose window should have a PRE tag but it doesn't yet), click somewhere and then use alt-[ and alt-] to decrease and increase the wrap width (initially 80 columns). Notice that when you change the wrap width, you get a stdout message saying that it's been changed, but the display doesn't change unless you force a reflow by resizing the window slightly. Forcing just a redraw doesn't help.

Probably was fixed a while back while doing some attribute cleanup

Fixed in the Aug 6th build.