I have been using Midnight Commander for a while and I have always been able to view the contents of a directory in each panel. I made some change that now the left panel shows the contents of the file highlighted in the right panel. How do I change this back?
Click/Select the "Left" menu item, then select "List...".
Or with keyboard only: Press F9 -> L -> L -> Enter or O
An easy way to revert most Linux apps to default settings is to delete/rename their user-specific settings directory and restart them. For mc that would be ~/.mc