Awesome little anecdote, thanks for sharing. I learned about reverse engineering because of UO. I reverse engineered EasyUO's technique for running macros which involved code injection and shared it with the world. Long live T2A!
So we would lure an npc to the house and set a macro to cast and walk 1 tile out of sight. Used regents but it was faster due to cancelling and the npc never died.
Likewise if you attacked an npc in a city but not hit. Then walk 2 screens away you could set an in game hotkey for attack which would trigger and cancel causing you to gain exp but not do anything.