Many experienced Wikimedia researchers (but probably not most) are vaguely aware that the edit history stored in the MediaWiki databases and derived datasets like Mediawiki_history is not entirely immutable. However, as far as I'm aware, this has been the subject of very little investigation and has not actually been documented anywhere! This naturally leads to questions from careful observers (e.g. T355182).

In June 2024, I investigated this history shift using the Editor_month datasets, which helped improve the "understanding While the knowledge is fresh in my mind, I should make it accessible by setting it down in a documentation page.