There's newsgroup discussion about a mind flayer sucking the brains
of a ghost, plus speculation that the fix for C343-121 has already taken
care of it. I agree with them that ghost's brains are too insubstantial
to be hit by brainsuck damage from mind flayers' tentacles. C343-121 is
vague enough to cover this; the corresponding fixes entry was more specific
and is augmented here.