In improv theatre it is a common rule that one person cannot counteract the ideas of the other person. It enforces the common goal to tell a story together. The request for revision goes very much against the sentiment, and I DO understand where it is coming from — After all it is all based on the narrators base effort to create a cohesive story. What I would suggest is a toggle for the overall story, so when you invite players you can communicate that there are no revisions and that everyone has to do his best to tell a coherent, cohesive story.