I'm not against ideas that are designed at keeping people safe (in fact, I love them!), but my input would be there's a few things here that I don't think were considered (this type of suggestion requires
a lot of effort and brainstorming), things such as:
- Will this actually be used/noticed by users? (If not, it's a lot of development time and extra clutter for nothing.)
- Can it be abused? (Most things can, but we deal with abuse cases extremely harshly, so it's not typically an issue)
- What happens if a case is cold? How long does it appear (wherever you are suggesting this to be shown)
- Wouldn't this incentivize a certain kind of behavior from scammers? Every step we take, keep in mind, forces scammers to adapt which changes the game.
There are probably a dozen other things I could mention, but I think I've made my point. Ideas like this are great, but require far more complex brainstorming and complex risk/benefit analysis to be considered.
Without doing that work to flesh out the idea more thoroughly, the best thing that can be done is people utilizing safe trading practices (which 95% of the site does not), following the rules (which are designed to keep things orderly and fair AND to keep you safe), and to use a mediator for larger trades (what is "larger" depends on person to person). The d2r mediations take literally next to no time at all; its super fast and ensures a safe trade.
At the end of the day, in the hiking world we have a saying that kind of encapsulates this scenario/situation quite well when it comes to bear containers for food storage in the backcountry:
"There is considerable overlap between the intelligence of the smartest bears and the dumbest tourists"
In this case, the general public becoming more educated about safe trading practices would do far more good than any tools that we can create and implement. That doesn't mean we don't try (I invest a lot of my time in building tools to help keep communities safe, and have volunteered here in the scammer accusations on d2jsp for over a decade), but just something to also keep in mind

People have to value (and want to) trade safely. Most people don't care enough to do so until it happens to them, and even then, some people still decide not to adjust their ways and end up being scammed again.