Overall, I'm not a fan of downvoting, but at present I definitely think it is a "necessary evil".

I believe that if the account was allowed to downvote, it would still be too weak to have a significant impact.

I think your team is on the right track with your semi-automated approach.

Thanks. It doesn't do anything too clever - although it saves any mistakes from switching between accounts.

All that the semi-automation does is enforce a few rules:

1. It only votes when voting power > 95% - ensuring the recipient gets the greatest benefit possible
2. It prevents votes going to other curators (who already benefit)
3. It prevents a single user receiving too many votes (percentage-based)

The primary reason is the aim of optimising the rewards for each user - we also feel that it's a much more efficient use of time if it follows our own votes (under specific conditions) - an idea that the Steemit Team could potentially implement themselves and save them from distributing Posting Keys each month!

I guess maybe they're leasing SP, too?

I don't think the Steemit Team's leasing SP. Those delegations are all over 5 years old (circa Hive split by the looks of things). I'm fairly sure SteemHunt's nothing more than a reward farm now too. It's somewhat depressing to see how those users are using the power delegated to them. When there are enough people doing better, more valuable things.