Hmm. Google is not the best example of what I meant but I think it's the same kind of box.

I've remembered one site which works like that. All the wikia have this in their forums but I don't think you can test it if you're not registered.

Here's a link to a screenshot: http://imgur.com/a/Uah5O

Here the 'window' pops up in the window I'm in and lets me go back to my comment or publish it.