On the "edit post" and "edit page" screens at the bottom of the main editor box, there's some text that says "Last edited by [display name] on [date] at [time]".
The date and time show when the page/post was last updated. The display name, however, appears to be for the last person that opened the page/post to edit. This inconsistency can be very misleading!
In the database, these pieces of information come from different tables. The display name is coming from the postmeta table, meta_key _edit_last. The date and time are from the posts table, column post_modified.
Please tell me if I'm just going crazy here, or if this really is a bug! Is it documented, or should I post a bug report?
I'd suggest either only updating _edit_last on post update, or alternatively just displaying the date/time last modified (and not the display name).