TL;DR - Allow moves to be reviewed/edited by everyone before final submission, per approval of the move author. Perhaps include co-authoring moves.

Generally, in a GM/Player setup, players only control their own character, while the GM controls all facets of the environment and NPCs. Storium is not like other games, though, since gameplay takes the form of writing. Players are, of course, not limited by the system to use NPCs or other PCs in their submissions, but they also aren't encouraged to, and trying to do so has some risk.

Only writing for one's own character can become very limiting, and can presents problems for things like writing conversations. However, as this is a collaborative effort, it would be bad form to take wholesale control of another player's character. Having everyone's character writeups available can help, but isn't enough to actively encourage creatively including more characters in each post.

I propose that moves be made available for review/editing in some fashion. That way as a player, I can feel free to include characters not my own when writing a move. This opens up the doors for creativity, and trying to engage with and understand more characters than my own. And I can do so without fear that I've written something unwanted, because that other player has a chance to review it and edit it accordingly if they feel their character would behave differently.

Hopefully, trolling isn't a fear, since people are here because they want to engage in collaborative storytelling. But revisions by non-authors would of course be subject to approval by the author. Perhaps as an additional safety measure, authors can flag sections of text as needing review by another player, and only that section can be edited by only that player.

I believe this serves the desire to collaborate as we write. It also allows Storium posts to be somewhat iterative, which is another important part of the writing process.