I am not sure if it's really necessary to limit post volume in that way. No one ever spams the thread singlehandedly to such degree (though I admit I have tried
). However, how about a simple rule that you can have no more than 3 (2? 4?) posts in a row? And an understanding that the post size limit is not there to break up the Wall of Text into 10 small chunks but so that what you say has to be more concise and to the point.