When I delete a rating I had one previously, it should no longer appear on my follower's activity feeds of me. The idea behind deleting a rating would be that it's no longer my opinion or accurate, or I just don't want it to appear on other people's feeds anymore.
Currently, deleting a rating still keeps it on my follower's feed, even giving it to new followers if the review was before they started following.
Ideally when rating something you should be able to set it to private just to allow for direct, not-public-facing feedback and account for this, or at least be able to set just your ratings to private.