When entities have armor on, they don't completely disappear, only the armor disappears.
If you stack chest_minecarts on top of each other, only the highest chest_minecart is affected. When the highest is removed, the new highest is affected.
It's really strange how some entities are or aren't affected. Arrows are, but snowballs aren't. Minecarts are but in a TNT minecart behind colored glass, only the minecart disappears with the tnt still being visible.
Okay, so f1 seems to always make some mobs disappear behind colored glass when entity shadows are off. When entity shadows are on, mobs don't disappear behind colored glass, but the entity shadows do disappear. Smoke particles don't seem to render behind colored glass in any circumstance. Other entities like arrows are also affected, with and without entity shadows.
Only seems to be on graphics fast and fancy, not on fabulous. Also only when entity shadow is off.
I've changed the title after finding out other mobs are affected. I've also added a crash report.
I saved and quitted to the title screen then loaded my save game again and the horse reappeared
Just to clarify, has this been successfully reproduced, in any version?