Hi. I experienced the same problem yesterday, where a reader not admin, not even connected saw a comment which wasn't yet approved (and wasn't their's).

 A staff member managed to recreate the issue while not connected, though we can't recreate it anymore. there was over 80 comments at the time the issue occured.
A clear of comment cache might have removed the problem
"Use Wordpress native Ajax functions" is unchecked
Cache is enabled
he is the link to the post Une professeure obtient la suspension de sa mutation à Paris

Thanks for your help.