You seem to be mixing different things. They do have an anti spam policy. I was talking specifically about spam. Non-spam is another matter. And who decides

You seem to be mixing different things. They do have an anti spam policy. I was talking specifically about spam. Non-spam is another matter. And who decides what is and is not spam, you might ask? Well Twitter of course; they just aren’t very good at detecting even blatant examples of it proactively enough to prevent it from detracting from the user experience.