When reaching through a 1x1 tunnel, the distance you are able to reach depends on the player's orientation.

What was expected: Reach to be the same for either side

What happened: Reach was five blocks one direction and six blocks the other.

To replicate: dig straight down ~3-4 blocks in survival mode and press up against the wall of the pit you dug. Hold the break button or screen, depending on the device, and count the number of blocks broken. Repeat this facing the OPPOSITE direction. On one side, the player will break five blocks, the other they will break six.

Screenshots: Each screenshot is a survival player facing the end of a tunnel, with the player as far forward as possible ( up against the border of the 1x1x5 tunnel) and pressing the break key. One block proceeded to crack and give off particles, as with breaking, whilst the other did not show any sign of breaking.