This is a fork of NoDamI by ProfHugo, allowed by the license (at least, if I read it right). All credit should go to ProfHugo, and all potential revenue generated by this project will go directly to ProfHugo. The mod turns off damage cooldown for most sources of damage, allowing each (rightful) hit to register.
This fork adds three extra options: an item whitelist, an offhand item whitelist, and an experimental "difference mode". The item and offhand item whitelists work as advertised: by adding an item's unlocalized name to the config, the item will give i-frames when held in the main or off hand. This is useful for weapons that expect i-frames to exist, such as a sword that sends out a shockwave or a shield that deals constant contact damage.
"difference mode" is experimental. When difference mode is on in the config, if one would receive an attack from the exact same source as the last attack dealt to it, while it is still flashing red from the last attack, this attack will be canceled. This is an alternative fix to the continuous damage problem, while still ensuring that multiple hits landed by different people on the same entity will still register. It is, again, experimental, so feedback is welcome.
Oh, also, in-game config has been added.