Dang, Kiwi, I can't believe that exquisite high grade stock broke like that! Chinese by any chance? That Chou wood, if it is like what they put on their rimfires, can be pretty soft and prone to cracking. As to fillers, I like what one old British writer said about a fellow who had to have a Best Quality shotgun stock refinished and complained that it had some filler in it. To quote from memory, "When you are dealing with highly figured wood, you naturally get a lot of knots and voids. It's inescapable. What worry when the master gunsmith repairs and makes them invisible in the finished product?" Voids are par for the course with many Chinese stocks. What you don't see, generally, won't hurt you. Of course, cracks through the wrist are another matter.
BTW, what's the Philips head screw for in the comb? Holding another crack shut?