Created attachment 8562225 [details] screenshot.jpg Was viewing bug 1127101 and saw the attached comment/change order - notice how the timestamps aren't in time descending order. (I have "display comments in backwards order" enabled). After leaving a comment on the bug, the order now displays fine. Guess it may just be when the last action was not a comment (eg remove a bug from "blocks")
I'm seeing similar behaviour in bug 1126176 - again it's a case where a non-comment action was made after a comment.