Version: (using KDE 4.3.1) Installed from: Ubuntu Packages Right now, messages that you have replied to have icons that indicate that you have replied to them. There is, however, no way of directly viewing your reply. Messages that have been replied to should have a way to take the user to the reply. This holds true for messages by others that are replies to messages that you have sent.
I wanted similar thing. But I went for a work around. By default my sent emails are stored in inbox rather than sent folder. This way, I can see the replies in thread.
I know this has already been reported, but I can't find the original report right now, so closing as INVALID instead of DUPLICATE.