That is not something completely "against the rules." A two-stroke engine can easily run backwards, the only difference is the timing of the engine is retarded rather than advanced. This means that it will make virtually no power and as soon as you hit the gas it will die. It is more common in airplanes where they use a stick to flip the prop over. It is common practice then to flip the prop backwards rather than forwards because as the engine fires, it will usually kick it back in the other direction, the correct way.

I assume you are using a starter box because a one-way bearing in a pull start or rotostart would prevent this. When you start it, try holdin down on the box a little longer instead of a quick bump. That will help get a forward start more consistently.