This was explained on Updates info.

Midas Touch was changed so now it only upgrades the item (instead of duping it).
* If you get lesser quality -> new item will be removed
* If you get better quality -> old item will be removed

But if you want to go back into old way, it can be done via simple GameUserSettings.ini tweak:
Under [JoanGodMod] change the defaut false value on MidasClone into true.

EDIT: I prefer the dublicate way, just because currently it deletes better gear (because of unknown reason where item durability is calculated into overal stats).

yes it basically compares both new and old and removes the one with lower quality. However ark system does not use real numbers to check quality, like how you admin spawn give items to yourself using a quality integer index. So further calculation was neccessary but its not very reliable.
This does make it harder, (and riskier), to upgrade using midas now. But at least it solves the problem of making players too powerful too quickly.
But server settings will allow u to change this back to previous way of keeping both old and new items. It's abit OP though, so if you're careful about server balancing keep it in mind.