We can give anonymous feedback about others where I work. We can submit it at any time about anything, positive or negative. I have never touched it despite knowing that HR doesn't get my name. It's not hard to figure out who's submitted a piece of feedback from their writing style and the specific situation you're writing about. Like if I were to give feedback related to working on a project with one other person, any sort of specifics about the project would make it very obvious that it was me writing the feedback.