Refresh S right?
I just took it apart again in my refresh S. The bottom is just a straight piece that goes into a hole, no clip. The top part is a clip. It's hard to explain, so I'll explain how it is installed..
The clip slides sideways into the bolster, then it's sticking out and you push the bolster into the car. To remove it, you should be able to pull some domination of straight out and inwards (toward the center of the car). Everytime I've pulled it apart, the clips comes out with the bolster.
I'm also tracking down the same rattle and it's hard, basically everything is loose so it's hard to tell. I just put some piece of tape on basically every part that touches, then will test again tomorrow.
People seemed to report that just putting tape or something on the clip the seat clips onto fixed it for them. Have you tried that? I think it partially fixed my noises, but I kinda think many things are rattling at the same time.
If you can't get it, let me know and I can go take it apart again and I'll take pictures this time. Might be worth a quick YouTube search too