Minecraft wiki entry for Development_versions, associated text: MC-13737 – Ridden Horse / Mule / Donkey duplicates when reloading the world.
MC-13774 – Mounting rideable entities (horses/boats/minecarts/pigs) underwater desyncs client/server (ghost mode).
MC-14944 – Weighted pressure plates' names are too long to be renamed.
MC-16413 – Boats toss the player off like horses.
MC-16828 – Horses make the galloping sound + their original walking sound at the same time.
MC-16847 – Horse jump bar becomes stuck if player is kicked off / dismounts while charging a jump.
MC-16887 – Jumping sideways on an unsaddled horse.
MC-17571 – Health overflow isn't removed when health boost ends.
MC-17675 – Sun jitters when time is set to zero and doDaylightCycle is false.
MC-17997 – Horse "Gelding" bug.
MC-18505 – Sitting direction does not fit when riding a horse.
MC-18522 – 3D anaglyth sometimes crashing Minecraft upon toggle in the options menu.