When I get an SMS text, reply, then get a re-reply, all three will be in my mailbox. However, the content of all three are on the highest (newest) message. I wonder if the device can be set to eliminate the earlier message, since the newer one contains the older one's content anyway? It would help reduce the number of "deletes" I have to do.
Unfortunately due to the design, the messages you see in the reply aren't actually part of the reply they are just the previous messages. So if you were to delete one of the older ones you'd also see it disappear from the newest thread (I hope that makes sence!)
What I find easiest is when Im done with a conversation is to just do a batch delete. Just hold the shift button and roll over the messages and hit delete.