MBaggese: click on the "crooked" arrow to the right of the message..
For me, I tend to keep the message loaded and type in the reply box. That way I don't miss something in my reply. Once I'm done, I'll highlight all of my message and copy it to the computer clipboard. Then, instead of clicking "Send", I click the "Back to Messages" button, then I'll find the message I replied to and click the "Quick Reply" button (see example, above).
Next, I'll position the cursor at the top of the text box and paste my message, then click "Reply"
This is just a "work-around" to the messaging bug. I, for one, would prefer to have a working messaging system (without changing my browser to "Maxthon" or "Firefox"). As the OP says, PLEASE FIX THIS!!!!! It's going on a couple months now with Chrome.