When I hit the “Edit” button after making a post on the forums, it almost always flashes the text for a split-second and then shows an empty box. If I hit “More Options”, it opens a new page that allows me to edit the post properly.
This is probably related to you using Firefox 23.01 or later ? That happened to me since I updated - have reported it a few weeks back, but it seems it's more of a browser issue sadly. I'm now on 24.0 and no change.
It's been a problem for me since my first post a month ago. You're right, it does appear to be a Firefox issue, as I can edit freely in Chrome without issue (I was using Firefox 23.0.1). Luckily, it's not a huge problem - the workaround is pretty simple - but a fix would be great when there's time, if it's not too time consuming. There are plenty of more pressing issues for the Devs to work on, and I just wanted to bring this to their attention.