Control characters breaks 'regular' font rendering
I pasted some cells from Excel into an Indesign text box. After that, the text rendering was completely distorted garbage text). Worse, I couldn't select the "Roman" font anymore, in any open document. Upon testing, that included many "normal" fonts like Georgia Regular, Minion Pro Regular and Warnock Pro Regular. I tried switching to International English MacOS and Indesign, I tried several versions from Indesign 13.1 back to CS6, and on Mac and Windows – same thing.
Finally, I discovered the control characters in the Layout text editor, and when I removed them (and restarted Indesign), everything was back to normal.