Call me crazy, but I don't think I've ever noticed this little field before, and I edit my posts a LOT. Is this yet another new hack? And where does this message show up in the post?
"Reason For Edit"
It shows up at the very bottom, in italics. And the hack is not that new, either...
That hack has been around for nearly a year now, although its a fairly subtle one. Originally though, edits made to your posts would not be mentioned in the signature area unless the edit was made some amount of time after the post was originally made. So you wouldn't see the reason left, either. And the vast majority of edits occur within the next five minutes after a reply is made, usually to correct misspelling, add some things, and fix grammatical errors.
Actually, as long as nobody other than you has viewed your post, you can edit it without that little thing showing up in the sig.
When you post there, it's a friendly wazzup to people reading your post that you screwed up. I can also use that in the forum i moderate to see what you editted... cool deal, eh?
Actually, it's just that the fact that you edited your post, along with the reason, won't show up if you make an edit almost immediately after posting. (I think the time limit is 2 minutes, but it might be 3.)