I had this problem myself back in June and pointed it out to my TAM. I got a reply back from Tina Lee that the JAMF Nation Team was working hard to tweak things to make the email digest better and they would report back when they had more information. I never heard anything further. Ultimately I stopped relying on the email digest and just scroll back through and read the messages from JAMF Nation directly.
I'm having the same issue. I saw another post on JAMF about this. Someone posted that they had the same issue and for them it was due to an auto reply they had setup. The auto reply stopped the emails from rolling through until someone on the JAMF team changed the setting on the back end. I'm not sure if that's the fix for everyone, but haven't heard or seen anything else on this.
@eleven Thanks for looking into that. There is another issue I noticed as well. Yesterday, I responded to a discussion of mine. However, it doesn't show up anywhere in the Recent topics when I'm in the discussions tab on JAMF Nation. Not sure if that's related or not. The thread in question: https://jamfnation.jamfsoftware.com/discussion.html?id=17834 which you'll note was commented on 11/18/15 at 4:57PM.
Actually this thread is another example of my last post. I just commented on it but yet it's not showing up in the top of the discussion list. At the time of this post, my last comment was made 8 minutes ago. So it would appear that even viewing JAMF Nation directly isn't really reliable at the moment in addition to email not working.
I noticed that my email settings where changed to Never, not sure why (I didn't do that myself).
So now I only get emails when I'm mentioned or an answer is marked, but not general comments. Might be worth checking settings to see if a site update on the backend caused this setting change for folks across the board.