We do check the content an author puts out before adding them to the Blacklist. It's how we identify the users who need to be added.
We can't manually verify all 1500-1900 uses of the bot individually each day. So if you have shown a history of posting content below our standards, we Blacklist you until we have seen a history of improvement.
We have found and asked larger accounts to avoid using the bot intended for minnows as well, and reputation score has nothing to do with that. We will look at SP or even average post-rewards. We don't restrict larger accounts directly, as the bot is available to any member of the community who has registered. We only ever ask them to consider saving the VP for the small accounts.