I just found that there were an unusual lot of suggested flags in the review queue. Only after going through it, I noticed that especially one case was weird: The question, answer and initial flagging have taken placed months ago (August 2012). I also noticed that Qiaochu Yuan had worked on the flagged answer as a moderator then (e.g. merged involved user accounts). Is all this possibly a consequence of him resigning from moderator? I.e. are we seeing a lot of his actions being re-evaluated because of that? If so, I'd think this is a bug ... Once approved by a moderator, the approval should not automatically be revoked by the moderator losing his status afterwards.
Nope, there is no mechanism involving "unresolving" flags handled by a moderator, once that moderator has resigned. There is no bug, either.
All that's going on is that someone is flagged stuff that had previously been "resolved", but someone thinks "No, it hasn't". For example, while that post author's merge situation has been resolved, there are still flags on it regarding that it is "not an answer". That Qiaochu took any action on it is completely coincidental, and I will also note that he is not the only moderator who looked at it back then.
I am inclined to believe all the rest to be of the same ilk - that is, there is something a user found wrong with the post that has persisted even after moderator intervention. This is a kind of thing that can happen even for moderators who are still around, after all.
If you still think certain flags are truly suspicious, I'm willing to take an extra look to see if there's perhaps a single individual behind things, but otherwise, I'm chalking it up to chance.