I can see now why more explanation is needed, than what I wrote above - the merge proposal on 15 Feb does seem an anomaly.
The "normal" reason for a rejected merge that is not listed in the change log would be, as I said, that it was marked as rejected at the time of profile creation.
If a couple of profiles are shown as a rejected match, it should not be possible to propose a merge as was done Feb 15.
It is also strange that after that merge proposal there is no rejection on record - which one would think there should be in order to create the situation where Philip had to remove the match in order to be able to propose it again.
I have just tested removing a couple of matches I created myself by marking them as rejected when I created a new profile in the place I'm currently working on. The removal of a rejected match showed up in the change log for both profiles, in both cases.
I find the terminology for discussing this quite confusing - I hope I don't cause more confusion.