Hey Cliffy,
It seems like the issue is essentially that if you change this option in the back-end of your site, everything works fine and the option is respected.
But that the checkbox on the front-end of your site does not work.
So the best way to share that is just to explain that fact to theme developer:
• When the checkbox is on display, you cannot check it.
• But the option itself works fine, so it’s just a display/UI issue with the checkbox itself.
• The error does not persist in a default WordPress theme so the Kriesi theme appears to be the culprit.
That should be plenty to begin with, I hope it helps!
— George