PROBLEM:
When a "teacher" or "admin" starts a "discussion" in a "Q and A Forum" and the "group mode" setting is set to either " visible groups" or "separate groups", then the "Reply" link does not appear to students. In all cases, the "teacher" is assigned as part of the group, though the "admin" was not. Perhaps this is how the "Q and A Forum" was designed to work, but I would expect that we aren't the only teachers that would want to start discussions within groups.

NOT A PROBLEM:
If the "no groups" option is chosen, then students see the "Reply" link, no matter who starts the discussion.
If another student in the group starts the discussion, then the "Reply" link is seen with no matter what the "group mode" setting is.

NOTE: I last updated our Moodle 1.8.2 in mid-September. Perhaps this problem has already been fixed.