We are on Jive 5.0.2 and last week noticed something similar. After some hypothesis and testing we figured out our situation.
1. We clicked Report Abuse on a reply to a discussion and sent the item to our Moderation Queue. Our process is to send a DM to the person letting them know why we flagged the item.
2. About 5 mins later we tried to go to the Moderation Queue to edit/redact part of the reply. It was gone!
Turns out that after a reply to an item has been sent to Moderation the poster can still see the reply along with an indicator that is it Currently Being Moderated. The original poster is able to Edit or Delete the item. This works out well in our case because we've sent a DM letting them know why we flagged their reply. In this case, our person just deleted their entire reply.
If an entire Discussion that has replies is flagged with Report Abuse, then the original poster or replier (is that a word?) doesn't see any of the discussion or reply while it is being moderated. This makes sense to me, because it's not clear which part needs to be reviewed and since the discussion has content from different members the entire thread is hidden.
Thank you very much Shane for your reply.
We are not experiencing issues with Abuse, or at least in our case I cannot say positive this happens with this pattern.
Anyway, that's a good starting point to check from now on.