Enchantment blast proction will reduce damage and the knockback in survival. Not sure if it is intented, but a high level blast proction armor created by command will invert the dirction of knock back. 

This inverted knock back effect can only be observed in survival mod, and not in creative. However, when a explosion occur near a creative player near end portal. Although the player does not show any displacement, it is teleported to the overworld.

Reproduce this issue:

1. Wear a armor with blast protection lv.32767 (not sure what the minimun level required is)

2. Place a ender crystal on one edge of the end exit portal.

3. In creative, fly and float above the end portal, also near the crystal. (It is possible to do this while falling as well).

4. Break the end crystal to cause an explosion.

5. The player got teleported to overworld while he didn't enter the portal visually.