Kroger changed their system to hard-deny gift cards from purchasing money orders.
All gift cards and temporary debit cards are excluded. Permanent reloadable cards with your name on them can still be used. In practice, system-denial will depend on the Bank Identification Number, YMMV.
This change affects all Kroger family stores as well, including Ralph, Dillons, Frys, Smiths, etc.
R/churning member ID4TgIOBi got a picture of the official internal memo announcing the change:
Hat tip to @telewatcr and MPD

