I think there are two different things:
1) Wearing an item to signal that you are a person worth talking to.
2) Wearing an item that makes it easy for someone to talk to you because it gives them a conversation starter.

At a night club I can see how a trendy khaki blazer encourages people to talk to you. I however don't see how it will encourage a person to talk to you while you ride the tram or are otherwise in a situation where talking to strangers isn't standard behavior.