It didn't get fixed when I restart Minecraft, but did when I restart my computer.
It was probably just some java error.
I believe this bug is fixed now.
I use the default minecraft resource pack, the default look and feel of Minecraft (built in).
The language I use is English (US).
Note that you need to jump high with your horse, long press space bar then release. The horse has to hit the ground, so that the subtitle appear.
It didn't get fixed when I restart Minecraft, but did when I restart my computer.
It was probably just some java error.
I believe this bug is fixed now.