Finally, thank you! @William Pai, that's exactly the reason. Maybe disable the ability to unsneak when hitbox would normally go through the block?
Another confirmation for 15w47c
This shouldn't be Works as Intended, this could be a map breaking bug. I'm currently making an adventure map where there is levitation parkour, but the player can easily get out of the room with this.
Finally, thank you! @William Pai, that's exactly the reason. Maybe disable the ability to unsneak when hitbox would normally go through the block?