I did much of this quite some time ago, as prequisite for a different
bug report about monsters vs shades, then set it aside. It ended up
being more complicated than I anticipated.
When deciding whether various non-weapon attacks might hit a shade,
hmonas() was not checking for blessed or silver armor that should have
been applicable. It did check boots when kicking, but not gloves or
rings (when no gloves) when touching, or outermost of cloak/suit/shirt
when hugging, or helmet when head-butting. (The last one is actually
moot because nothing with a head-butt attack is able to wear a helm.)
The problem was more general than just whether attacks might hit and
hurt shades. Various undead and/or demons are also affected by blessed
and/or silver attack but weren't for non-weapon attacks by poly'd hero.
At least two unrelated bugs are fixed: a rope golem's AT_HUGS attack
gives feedback about choking but was fully effective against monsters
which fail the can_be_strangled() test. And it was possible to hug a
long worm's tail, rendering the entire worm immobile.
The report also suggested that all artifacts be able to hit shades for
full effect, but by the time shades are encountered everyone has an
artifact so that would nullify a shade's most interesting ability.
TODO: monster against hero and monster against other monster need to
have similar changes.