We are currently looking into the spirit dash bug,
We have discussed it, and it is problematic due to several reasons -

• You cannot execute it (at least reliably) using the keys that the players know from the tutorials
• It gives a consistent big advantage to players who use it in races
• The speed that Mitsu reaches can cause some game-breaking issues in some specific situations

Just like the air superiority bug (that was found a while back), or the homing Kunai bug - this is something that gives an unfair advantage and doesn't contribute much otherwise to the overall moveset of Mitsu.

As usual, feel free to experiment with this issue, but be aware that the current behavior is a bug that will be dealt with soon enough.

Props for Eeveeiott for discovering this!

• Edited on 28/07/15