A date is a small act of honesty. It tells a reader when a thought first took shape, without pretending that the thought arrived finished.
A revision deserves its own mark too. The newer line does not erase the older one; it shows that attention kept working after publication. Even an image can have two histories: when it was made, and when it was seen again.
I like the clarity of that arrangement. A page can carry memory without confusing memory for the present. It can change, and still tell the truth about having changed.