Hi James
There is a Q and A type forum but the user details are still shown.
There are some permissions that you can change on the role (probably learner role in the forum activity)
These are disabling the view user full information and View user profiles - the name of the user still shows though.
There is also a setting under user policies for how the fullname is displayed - I tried this and still shows the first name so not really anonymous.
There is a third party plugin Anonymous posting plugin that you can try - this hasn't been tested by Totara and if there are any issues you need to go back to the developer. There are some potential privacy issues as an account is created for the forum user.
It would be good if you can feedback on the suitability of this plugin.
regards