With regard to Reddit's policy on transactions of certain goods:
External links to firearm vendors holding a Federal Firearms License are not in violation of this policy. However, links to vendors without an FFL are prohibited (this would include links to gun shows or other sales or listings, online or offline, where vendors do not hold an FFL). Direct user-to-user transactions arranged on Reddit for firearms or ammunition are also prohibited, regardless of whether either user holds an FFL.
This policy does not impact goods that do not meet the ATF definition of firearms or ammunition.