Here's a recipe for confusion:
Load a page on Stack Exchange.
Do anything that updates the page via JS―leave a comment, vote, etc.
Leave the page by following a link.
Use the browser's back button to return to the original page.
You'll be unpleasantly surprised to find that all the updates from step 2 are gone. This is really confusing, and it wasn't true two weeks ago. It's a major usability problem. I assume it's due to the
Cache-Control header changes, since I first noticed the problem on either August 5 or 6.
Leave a comment, click a link, go back, and the comment is gone.
Stack Exchange used to provide users with updated pages without making them hit the reload button all the time. Now several times each day I have to figure out the page is out of date on my own and hit reload. It's confusing every single time.