The Bug

Signs render in front of the eyes of invisible endermen, even if the sign is much further back.

How to reproduce:

1. Spawn an enderman
2. Push a boat into him so he won't wander
3. Stack two blocks behind him and place a sign on top
4. Look at the enderman and run this command:

   /effect give @e[type=enderman] invisibility
   

5. Walk around to position his eyes in front of the sign
   → Notice the sign renders in front of the eyes