One of the usability criteria given in bug 103711, `Usability for 1.0', is `Every UI element does something useful'. Therefore, if bug 959 (Accesskey attribute not yet implemented for XUL) is not fixed before Mozilla 1.0, the underlining (or whatever special style is implemented by particular themes) for access keys should be removed before 1.0. Having things which looked like access keys, but which didn't function as access keys, would be worse than not having them at all.
Since bug 959 has been fixed this bug can die. -->WONTFIX