do you allow members to advertise their forum on your forum? in what way?

i allow members to have a link in their signature, and there is a specific forum for links (only if they link back to us on their forum in some way), and every 2 weeks i choose two of these to be added to the links at the top of the forum

i do not allow advertising in any other parts on the forum, and i dont approve of pm advertising (it says not to in the rules, although there is no way i can enforce that unless members report getting spam messages).

all links advertised on the forum must not contain anything illegal or anything that is unsuitable for the younger members of the forum