Not sure if it's a bug, or just an irritating feature.
When I attempt to close a tab of a ComicVine forum topic, I get the message:
"This page is asking you to confirm that you want to leave - data you have entered may not be saved."
Along with two options, "Leave Page" and "Stay on Page".
This is a pretty helpful feature to have, if it had appeared when you've entered content in the text field (as on the old site)...the problem is that it now appears no matter if there's any text there or not, making it a rather inconvenient feature.
(This problem does not seem to appear on locked topics, presumably because there isn't any text field there.)
Browser: Firefox 19.0.2.
System: Windows 7.
Edit: It works correctly in Chrome (where the warning only appears if the closing tab does contain text in the input field).
Further Edit: By systematically disabling my Firefox add-ons, I discovered that it is YouLoop that seems to be causing this (somehow?). With that add-on disabled, the warning only appears when actual text has been entered in the input field (as it should).