I don't really mind whether its simultaneous post by post, which is what I have experience with, or a collab between combatants. I think a unanimous decision to do one or the other has to occur though as post by post will take longer, probably, than a collab.

In terms of combat rules, I'm not so sure. In the past I've been very relaxed about it and no harm ever came of it. Plus, to every fight there are 6+ referees, shenanigans are going to get caught. 

Things I've seen a bit of though are total posts/lines for a particular move determining its effectiveness between two equally matched opponents. Obviously, no forced hits, the opponent gets at least one post to write a rebuttal.