WordPress.org

I can't rate?

Administrators are not supposed to rate their own content. However, if you feel like doing it anyway, just logout from the admin panel, and you should be able to either dislike or like your own posts.

Can my visitors do more than like/dislike?

No. That's the point. Visitors can either like or dislike your posts. No compromising or "Maybe I think some of it is good, I just don't agree" stuff. Like or dislike, that's it.

May anyone rate a post more than once?

No... What's the point of that?