Can you show me the spot it is posted under rules, that Outpost is a place you need to check for Rep.

No trading with scammer alts. We do not encourage our users trading with scammers, and you should be careful to not trade with obvious alternate accounts of scammers. Please check the user's Steam profile and SteamRep status before trading with them.

Please check the user's Steam profile and SteamRep status before trading with them.

Steam Profile and Steam Rep, nothing says you have to check there Outpost, not even a suggestion to check.