The Bug:

You can produce particles whilst inside of powder snow, despite not moving at all.

Steps to Reproduce:

• Place a rail.
• Place some powder snow above it.
• Place a minecart onto the rail.
• Destroy the rail.
• Get inside the minecart.
• Move forward.
  →  Notice how particles are produced, despite yourself not moving at all.

Information:

As far as I am aware, particles from powder snow should only be produced when there is some kind of movement.