PSGML mode should not override 'M-BS'.
Daniel Pittman writes:
The new PSGML mode has, in it's keymap, one stunningly
counter-intuitive
binding[1].
The Sequence Meta-BackSpace is bound to `sgml-mark-current-element',
rather than the standard `backward-kill-word'. This caused me some pain
until I went and fixed it.
fortran mode too, if i can remember exactly...