The default action on our support system (which we did not develop) is to "Reply and Close".
I believe Tender designed it this way because, at least in our experience, 99% of the time after we reply, we never hear from the OP again. So by always closing the discussion after we answer, it keeps our queue clean and lets us clearly see what discussions are still open awaiting our response.
Anyone can always re-open the discussion if they feel they have more to add. It's not meant in any way to try to discourage discussion. We could just delete it if that's what we had wanted to do. :)