I'd like to see the [Private Reply] link made a different color, or moved far to the right side of the "button" list, or, eliminated entirely, with private replies handled via the posting screen. It shouldn't be too difficult to craft a workable layout, a la the Agent newsreader's methodology.
Basically, you'd decide at posting time whether you wanted your reply to go to the group, to the author, or to both. The default would be to reply to the group. Thus, anyone wanting to reply to the author would have to make the conscious effort to check the "Send to Author" (or "Both") option button before clicking the "Send" button. This would completely eliminate the possiblity of inadvertently sending a private reply by clicking the wrong link.
As a stopgap measure (read: "if nothing else"), can you make the Private Reply message editor have a colored background and blaring headline saying "PRIVATE REPLY"? As it is now, the two editors are virtually indistinguishable when one is focused on composing and submitting the message. (Requiring people to carefully discriminate between two near-identical interfaces (with very different outcomes), and requiring them to read the label on two identically placed buttons, runs counter to most ideas of intuitive design that I'm aware of.)
Just a combined IMO/plea for help!