5 posts per day target is far too little. It's just going to completely disincentivize curation.

I really don't see them implementing a this without adding a way to scale down the power of your vote for each vote. If that's done, I'm really quite confident that it'll help incentivizing organic curation over bot curation.

Some ideas - enforce time limits, i.e. 1 vote per minute - something that'll clearly catch out bots over normal users.

1 vote per minute really wouldn't do much. At ~40 votes per day, that's about 1 vote per 36 mins. Even taking into consideration peak times where most posts are published, the odds of an "upvote collision" are fairly low. If anything, bot owners will only be forced to add a line of code that waits an extra minute before their next upvote. Make that 2-5 mins and you start seriously interfering with user experience, some posts are pretty short. Also, 1 min/upvote is a problem when considering comment upvotes, you'd have to start considering both as different. Not a fan of the rate limiting idea, I'd rather have lower influence/reward for voting more than having to wait.