The menu says that when you set the anti-shock to “0 seconds” that causes the camera to use electronic first-curtain shutter (EFCS) for speeds of 1/320 second or less.
However, I often (not all of the time, but often enough that I’ve noticed the pattern) have images ruined by shutter shock when the picture is taken at 1/320 second. For example, the 100% crop shown above was taken at 1/320 second.
I have a theory that someone mistranslated from the Japanese, and that the Japanese menu has the correct instructions, that EFCS is used for speeds of LESS THAN (but not including) 1/320 second.
Anyway, it’s very annoying that this happens. I don’t think I’m pixel peeping either, the image looked unsharp even when I was looking at it scaled down to fit on my monitor. I hope this is something that Olympus fixed on its newer cameras.