Why not just require mod sellers to use their real name and have a working phone number? Any kind of "certification" means you are providing some level of guarantee that it works with Dolphin - are you sure you want to do that? Then you could charge a small fee for "listing only".
Boonex buys mods and list in market and admins buy from boonex market - thats cool
support by modders, reviewing the support, the modders can earn grades
support by modders, reviewing the support, the modders can earn grades