So imho any disclaimer you guys are discussing should appear not only when you register but also when browse as a public guest. I feel
IIRC, the newie flag warning is shown to newbies and members below a certain number of days logged in, but for this to appear the member needs to already have active flags. Not sure how effective it is at this time and more policies to protect members from scam would always be welcome; Maybe a warning at the top of certain boards (visible to guests and members) where trades are more likely to happen.
Additionally I expected the scammer to get at least be banned quickly and was astonished that despite countless reports and proof (even crisp video proof at one point) no action was going to be taken.
Scams are not moderated, so the mods cannot take actions against scam posts or members who make them. There has been lots of discussion about whether to moderate scams and the consensus seems to oppose it as it could give users a feeling of faux security that any unhandled case isn't a scam.
The DT system is in place to warn against scams, but as all systems, it's not a 100% efficient.