This has been discussed in the past and while I am biased since I sell my signature I dont think thats a valid option unless there is no other way. This would have to include referal links as they are somewhat paid signatures. A more difficult case would be doog's signature for his own casino just-dice. Would that be banworthy? Its a paid signature in a sense as its advertising for his own casino and he is earning money off of it. How about e.g. SaltySpitoon advertising their sales thread, is that allowed? As you can see this will not be easy to draw the line.