No idea about the issues with Firefox, that one works fine for me!
I got a great tip a few days ago though. When posting you can click on the button that looks like a light switch in the top left. That reverts the posting window to plain tekst, all other buttons including smileys etc. are disabled though you can html-code. But even better is that it can get around wonky browsers. Like my required work IE browser I'm using now that doesn't allow the 'enter' command to function when typing.
So the above white-line was made possible by 'flipping that light switch', and I can subsequently switch it back on and insert a ninja smiley for which I don't know the shorthand code, like this!