I have added an additional feature to the revision history. On top of the revision history, a complete list of all events like created, edited, retagged, recategorized, hidden, reshown, closed and reopened is displayed. Like this it is now completely transparent to all users what happened to a post on PhysicsOverflow. These events are visible for all posts written since the eventlog has been installed (2014/03/06).
If the content of a post did not change, for instance in the case of recategorization, the revision history stays to be linked as "no revision", but the event will be visible if you click on this link The reason for this is that the very large eventlog database table would have to be queried for every post in a question thread to get the information about such an event. This would delay the page for about 3 to 5 seconds, depending on the length of the thread, which I wanted to prevent.
Another exception is automatic retagging by the Tagging Tools plugin by Scott Vivian, which is not logged in the eventlog (appears as "retagged by anonymous" or just "retagged xx days ago" or similar).