> Now that I played around with it, I'm OK with how it works, it's just the "Private" isn't very intuitive. Could it be labeled "Private Reply" or something like that? Just thinking out loud.
My issue is that if you ask someone who has not sent a Private reply before to send a reply to sender, many, probably most, will conclude the functionality is not there and so send a message via the group asking for the person's email address. It ought to be a bit clearer that the greyed out Private button does activate this functionality.
I think there are three things combining to make it hard to find on a large screen:
It being in grey means it does not stand out, and why would you press a disabled button which it looks like?
It is way over on the right, a long way from the two buttons you are looking at.
Most people on our group would be familiar with Reply to sender or Off-list reply, but private means little to them.