Ever open up an entry in a tab to comment on later, come back to it two days later, and submit your comment, only to have the comment eaten by an "invalid form submission" error? From now on, you won't lose the comment entirely; it will get displayed underneath the error message so that you don't have to risk losing the text of your comment when you hit the back button.

This is so awesome!

Although I hope it doesn't mean I get out of the habit of copying my lengthier comments on LJ and thus lose them more often. D: