bump.

Why not have the user's login name somewhere ?

I dont recall ever logging into a software package and not displaying my logged in username.

Is there a logical reason to do this ?

Please read wpForo documentation. I'm sure there are dozens of wpForo functions and features you don't know yet. wpForo has Online Members widget in Dashboard > Appearance > Widget admin page. You can put it in forum sidebar.

https://wpforo.com/docs/root/getting-started/forum-sidebar-and-widgets/wpforo-widgets/