[@Gowi][@tsukune] There's a balance between back-and-forth and collab.  The way I find that works best is allowing people the flexibility to tailor post length to the situation.  Maybe one post has a bunch of internal thoughts and several different actions.  But another might be a single line, a single action, or OOC you've mentioned that the other guy is free to interrupt and change the entire course of what follows.  With enforced lengthy posts, it almost feels like you have two or more conversations happening at once.  The first part and response to it, the response to some actions, and the response to further actions or dialogue.  And this is absolutely confusing and choppy and senseless.  Not to mention then the first person has to go back and respond to the first response before even taking the second action from the first post and....@.@  We don't need to cover the same action five times.  Once, /maybe/ twice.

I believe that OOC communication is key.  "Yo, if I do this, would you do this or this, or something else entirely?"  That lets me know that I'm predicting reactions properly, and the action would proceed more or less how expected.  I can weave reactions to things that the other guy hasn't actually done yet into my post and keep going.  It also helps to figure out what will provide the maximum amount of fun for all parties involved.  Willingness to change things if someone goes "well no you couldn't do that because I would have done this and then you really couldn't or at least it wouldn't make sense" is also important.  Like...someone tried to grab and bite a character that I mentioned could teleport.  Grabbing him is fine.  Stabbing him would have been fine.  But the amount of time the entire hold&bite action took was longer than he would have stayed put without popping away.  So I mentioned that, switched the character that was grabbed for someone else, and we kept going.  If there hadn't been anyone else we would have found a different solution.

It's one of the drawbacks of more than one person writing that unless you give one or the other the final say, there's going to be breaks.  But I think that those -- even serious ones -- are worth the extra input, so I try to be flexible.