I often leave negative trust feedback for scammers before they scam anyone, or after they scam others. I don't often get scammed myself.
Perhaps the wording next to "negative" should be changed from "I was scammed" to "this person isn't trustworthy".
Sounds like a fair suggestion in my opinion since its a good change in wording.
It's possible for people to be suspicious from the start and it doesn't hurt to be proactive in preventing fraud since it's not always "I was scammed" but I am preventing people from scamming / their intentions are suspicious to me.
If you flag them before they scam, potential victims are alerted by the "trade with caution" note next to their posts.
If you wait until after they've run off with all the coins, it's too late. By then they've made a new account and a new scam thread.
Seems daft to me to only allow us to leave negative feedback after the event, and only if we were personally scammed.