Users of the site Digg will know how the commenting works. It allows you, through a series of Ajax calls and other information, to edit the comments that you've made for a certain amount of time right on the page. It's a handy feature, and in this new posting over on Spindrop.us, they show you how to create it (with the help of symfony).
It's pretty straight forward. For all of your posted comments you check if the owner of them is viewing them within 3 minutes of posting the commen. 3 minutes is usually enough time to notice you made a typo, but if you disagree I'll leave it to you to figure out how to adjust the code.
For example, I make a comment, realize I spelled something wrong and then I can click on my comment to edit it. Of course using AJAX means this all happens without having to reload the web page. Therefore the edits are seemingly quick. So let's add it to any web site.