Placing a dark steel armour item into the hotbar, then selecting and right clicking on it should equip that armour item. So far so good, this works as expected. However, it is also creating a full copy of all upgrades applied to that item and placing them in inventory. This action is repeatable, so it is easy to flood your inventory this way, as well as side-stepping creation costs for upgrades for your friends.

Apologies, this behaviour was observed in Ender IO v.5.52.

And if there's a inventory upgrade, it duplicates everything placed there too