Are you suggesting that posts should have version tracking, or something more complicated than that? Like: Updated by jaybonci, 2003-02-28, automatically?
Your suggestion is kind of vague. How would you envision that working?
Maybe the person updating their node could check a box like the "This is a significant update" box on the home-node editing page. (People do seem to stamp their updates pretty consistently without automation.)
Just simply along the lines that a person hits submit, and the updated message appears. Might I add that it probably would need time as well. So after the post, he goes back and changes something else, the date and time would get updated.