Merit can't help someone to scam because it's meaningless for reputation, anyone will look on his feedback to know if the account is trustworthy or not. Based on this case the account only have 4 activity which is he can't rank up since he need to post more and he can only rank up to Member rank. Since signature campaign mostly accept full member rank, I think this matter isn't really that matter. It's a different case if he haven't earn any single merit and someone give them 5 merit since the campaign requirement need at least 5 merit in 120 days to apply the campaign.