I have the same problem as palatino and could not find it in the forum after looking for hours and therefore posted my own bug report.
I tried so many things, I used CKEditor versions 3.6.2.4 and 3.6.2.5, deactivated all plugins, and activated one by one and found the problem to be with W3 Total Cache. I get no comment editor, it’s invisible like palatino described it.
Thanks to palatino I know at least that if I disable js minification it solves it for now but caching and page loading speed is really important, so I will be eagerly awaiting the fix or consider some of the other WYSIWYG editors.