Just have the attachment only affect the first 3-5 rounds of a trigger pull. That way people who control their fire rate would see the benefits of less kick, but when they hold down the trigger the recoil will get harder to manage (as it should) after about 5 bullets of full auto. (Yea, I know it's not realistic... but we're going for balance, not Mil-Sim)
Further ideas are to have the compensator be less effective in the 1st second after a player stops sprinting, and to make it more effective (a few extra bullets before it becomes less effective) for people prone or crouched. This bit would counter the "run" part of "run and gun" and promote more crouchwalking and ambushing, rather than just everyone sprinting everywhere like they do now