I see a benefit for a separate thread and a disadvantage as well. The advantage is often when a person comes back and the thread is full of 1 ~ 4 sentences per post of sex dialogue it can be mildly annoying to read through and pick out the bits of information that actually relate to the post you need to make. The down side is it might get lost and harder to find, or people might not remember to switch over and something important might have been said during it. I am fine with either I merely am noting the pros and cons of each.