Lastly, don't bring in those that will constitute nuisance, this forum is well-moderated and different from random social media platforms.
Anyone bringing a nuisance to the forum will automatically be a nuisance himself, because that is the least I could think of right now. Although the person who invited another or introduced such to the forum is absolved of any faults from the person such a person invited because they can't control their behaviour, and telling someone to come and learn and probably make income here is harmless on its own.