Many newer keyboards have web-navigation "hotkeys" in various places (Thinkpads have them near the shift keys.)

If you've put a lot of effort into writing a new issue or comment, and accidently touch one of these keys, you will lose everything you were typing, because trying to come back to the page is a re-post.

It would be (IMHO) a very easy change to add "onunload" handlers to any new/edit page, which would go through a JavaScript confirmation asking you if you want to leave the page without saving your changes.