This totally mystifies me.
After fixing a bunch of issues around using NSAttributedString and CCLabelTTF, one thing still is not working despite me trying to track down the issue.
Using NSAttributeString, you're supposed to be able to add images as NSTextAttachment and have them displayed inline with the text. This works fine with a UILabel, but something in the CT rendering breaks things for CCLabelTTF, so that NSTextAttachments are simply skipped (shown as spaces on iOS, placeholder [OBJECT] font glyphs on OS X).
It's as if image rendering is somehow getting disabled, but I can't find anything in the code that appears out of place.
Initially I suspected the various hacks done to the attributed string before display, but even feeding the draw routine the simplest possible attributed string (a string only containing the image attachment) fails to work.