That piece is a locating pin, not part of the main threaded mount. On many camcorders, there’s a small matching hole near the tripod socket. The pin fits into that hole to stop the camera from twisting and to keep it aligned facing forward on the mount. Many still cameras and compact cameras don’t use this anti-rotation system, so on those models the pin may do nothing except get in the way. If your camera doesn’t have a matching hole, the pin isn’t needed for mounting.