That is a good thought...I just went and took a look via putty (with a couple different fonts), and then on the actual Retropie box (by quitting emulationstation), and I see substantially similar stuff. On the console itself, the diamond-question boxes render as solid squares. Putty was even less helpful, yielding:
pi@retropie:~ $ ls ??? fstab-backup ????LE RetroPie RetroPie-Setup es_input.cfg.bak ??"?GNSO ȯh retropie-backup.sh x?1?XX
The files themselves have weird contents. This time, they've got stuff like this:
pi@retropie:~ $ cat x?1?XX Sd55d:01:N/A Sc03c:00:N/A Sd636:00:N/A Sda3a:09:N/A pi@retropie:~ $ cat ??? SC8ade:a5:c6:N/A SC987c:a9:c6:N/A
I'm not familiar with numbers in this kind of format.