I am playing on a Realms server vanilla survival world map that was upgraded from 1.13.2 to 1.14. This world map has been consistently upgraded to each new version over the past several years.

While the Hero of the Village and frequent trades (reputation) both display a discounted price, the discount is not actually applied in any trade with any villager. I've tried this with newly generated villagers in new chunks, old villagers, and bred villagers.

For example, say a Mason has a default stone price of 14 stone for an emerald with a discounted price of 13. The villager will only accept the trade if I have at least 14 stone in the trade slot.* When the emerald is taken from the right-hand slot, a single stone is left in the left-hand slot - as if the discount was applied. This is a "ghost" item: if that stone is clicked or the trade GUI is exited, the stone never appears in the player inventory. Thus, all 14 stone are consumed and the discount is never applied.

*If 13 stone are placed in the left-hand slot, an emerald appears in the right-hand slot. When the emerald is clicked, the villager makes the declined trade noise and the emerald remains in the slot. Even stranger, it is possible to visually "lock-out" the trade by repeatedly clicking on the right-hand slot emeralds or items. The panel on the left displays the red X over the trade. Again, this is only visual; exiting the GUI resolves this visual glitch.