I'm actually of two minds with this.
While on the one hand, I really dislike ill-edited and inaccurate posts (they personally drive me up the wall), on the other hand, not everyone has the time to personally clean up every post. For that matter, a large number of posters do not have English as their first language, and you'd be penalizing them unfairly. Remember that the board are supposed to be fun, so as long as you not ruining it for others.
My compromise suggestion would be that maybe you can require clarity from any "official" posts. That is, legibility could be a requirement for eligibility as a "reference thread". That way, the majority of people can have their fun, while the core threads will be easily readable.