It is not a problem , it is quite a sensible rule in my opinion. I asked niallist to vouch for me on there even though I have 270 positive feedback on here.
The excellent moderators on UKscenario look out for their members as we do on here , we even exchange info on problem members of both forums. They ask for a new seller to have an existing member of the forum to vouch for them so people don't just appear offload their kit and disappear again with nobody having a clue who they are.
If you have dealt with a UKscenario member on here ask them if they would be willing to state your sale/trade/purchase went ok.