I interpret you as meaning that if some had 'flash' their posts would be considered as better than their actual merit (correct me if I'm misinterpreting). If that were to be the case would there not be an equal or stronger effect from a poster having a good reputation or a gazzilion karma (like Luke, Alicorn or Eleizer) under the current system?

There would also be the question of whether if this effect exists it is sufficient detrimental to outweigh the motivational benefits.