With 7.2 blizzard introduced Empowered Traits for artifact weapons.
Every AP empowering item collected before upgrading your artifact becomes useless.
I can't find the place where the message "your weapon is too powerful to be modified by this item" is generated.
Does WoW really store the acquired date for each AP boost item on the server and compares it or is that check something we can find in the client as well?