If I'm not logged in to any Stack Exchange site, I can give feedback clicking on vote button:
But if I'm logged in, and I have less than 15 reputation, I get a message that more reputation is required:
All I can do is to log out and give feedback.
But for me this is not logical. If someone does not have not enough reputation, he/she should be treated as unregistered one, being given possibility to send feedback instead.