Can this still be done? I don’t see a mechanism to do this any longer.
OT: How to respond to someone vie email, or privately
Nope. The lawyers for TMF decided that they should not turn this feature on when they migrated to this new Discourse platform.
Are you familiar with the platform that @Manlobbi created that has lots of former features? If you sign up over there, and the person you want to talk with also signs up, then you can privately email them.