I'm not being sarcastic, I'm trying to understand what you mean by "associated reply" because posts are made to the thread in chronological order, the first post up top and the newest post at the bottom. Replying to a post "in the middle" so to speak will quote that post in your reply, but your reply will go to the bottom of the thread. If you JUST reply, or if you delete the quoted text, your post goes to the bottom of the thread.
I'm replying to you here, and I've got your post quoted.
ETA: Ok, so I "dismissed" the page by going to page 1, but I didn't clear out the reply box. And there WAS no reply box on my screen. I clicked "Post Reply" hoping to open the reply box, and it posted the message instead of bringing up the reply. In this case, the Post Reply button sent whatever I had left in the box instead of giving me a new box (even though I left the page.)
Is that what you're talking about? Because I can see how that is problematic. I'm going to see if there is a way for us to fix that, and at least display the reply box if there is data stored in it to post.