We utilise the SteamRep API to automatically ban any user who is tagged as a scammer on SteamRep. Claiming that scammers are "allowed to use the scrap.tf auction system" is quite a loaded statement. It misses the unfortunate reality of the situation that SteamRep will always be behind the curve, because it is very easy for scammers to create a new account, funnel their items, and evade their bans in the time it takes for SteamRep to catch up to them. We (the staff) simply do not have the time to be proactive in hunting down scammer's alt accounts, however, we will investigate any account brought to our attention -- which is why, if you are concerned about the legitimacy of an auction, you should use the "Report Auction" functionality and describe in detail what those concerns are. Alt accounts using auctions is not our intention, it is a symptom of the difficulty of preventing fraud.