The thumb studs are 2 pieces, a male and female side. The post has splines that fit into the female side, and they are pressed together.
It can be removed, but not easily.
I was peening a pivot on a handle that I had swapped the blade for one with the thumstuds.
The thumb studs came apart from the shock from peening the pivot.
They went back together and stayed together with just a light tap from a hammer.
So they can be removed, but they are not threaded.