ToME WikiKhymChanur: If we had most forms of HP healing (as opposed to regeneration) use the healing "damage" type, the we could do interesting things by having equipment and timed effects granting resistance or "vulnerability" to healing. Resistance to healing would be a good property for cursed egos and artifacts, or as a means to balance out otherwise too powerful items, while objects that gave vulnerability to healing would make valuable objects in their own right. Plus a trap or monster spell that temporarily made you immune to healing would be really nasty.
LordEstraven: This is an... interesting idea. I'm not sure if it would work in ToME but it sounds like good module fodder.
BucketMan: Seems an appropriate modifier for undead subraces.
DarkGod: I like that. At least make healing use dam.HEAL, so we have the possibility to do it if we want to.