You may be missing something here and there.
1. I do have address (actually 2 addresses) staked, still, when I want to do things, I usually do on completely different addresses so I don't reuse that much. Would that make me a scammer? I hope not
2. Knowing the fact from point 1, nobody stops a hacker (especially the hacker of a long inactive account) remain with this badge and still use a different address.
3. One can make a new account and stake his address and might be (wrongly) seen as reputable.
So.. I think that this kind of badge would not help. It could even mislead. The proper rules for engaging in trading on the forum are:
* Read carefully all trust feedback no matter who made it, then decide for yourself.
* Make proper use of reputable escrows.
* Avoid impersonation by avoiding other messaging platforms and by using and requesting signed messages (and here the staked address will help).
I think that this is more appropriate for Meta.