See the master bug (10165) for login instructions Click inside the editable area, press one of the toolbar buttons, like Bold The caret is removed and nothing happens (if you click back inside the editable region and start typing, text isn't bold). This only happens once, you'll need to reload the page to see it again.
This appears to work fine with Tiger WebKit, marking as a regression.
<rdar://problem/5072321>
Looks fixed.