People doing revert analysis and stuff might be interested in this: https://bugzilla.wikimedia.org/show_bug.cgi?id=56849
It turns out, for some time we have been failing to detect edit conflicts if the two page saves occur within one second of each other. The second save will silently overwrite the previous edit, because it derives from an earlier parent... but the parent_id recorded in the revision table will incorrectly point to the conflicting edit. So the edit will look like a reversion plus some editing.
G'luck! -Adam