I set up something with water and signs (to block the water) over the void in the end (so it would be too far away for endermen to teleport to or from where I was building). I noticed that something strange was happening, and realized that Endermen can teleport onto signs.

I made a new test environment like in the screen shot and spawned an Enderman onto the endstone. I then shot arrows at it until it teleported onto the sign on the cobwebs. I'm pretty sure that Endermen are unable to teleport onto ONLY cobwebs, so they must be thinking they can land on signs when they can't.