Title self-explanatory. If you equip an item known to be cursed (possibly because you hit the wrong key), you should be prompted to make sure you want to do this.

Possibly a similar prompt for other known-harmful items: potions of (reduce attribute), cursed scrolls of chaos resistance (when those exist), and so forth.

Obviously the prompt would need to check ID'd status - although a prompt against using any sort of un-ID'd item should perhaps be available as a user pref... I'm going to stop before I make this RFE too long.