FWIW, unless you are doing extensive night shooting, a flash hider on a .22 is essentially cosmetic. Even at night, the muzzle flash from a 16" .22 barrel is minimal, at best (or worst, depending upon your outlook).
Yes, the threads are 1/2 x 28, and unfortunately for those that shoot suppressed, they are akso the same length of .6in instead of the shorter rimfire length of .4.