Thanks for clarifying on the dust-vote limit. Perhaps a bottom threshold of 25% or something might have achieved the same purpose.

"Just because it's rewards that busy would have taken anyway doesn't mean it doesn't create a "reverse funnel"."

I'm a little unclear on this part. Busy doesn't assign beneficiaries to posts (as far as I know), so they don't take a cut of any posting rewards. I think they pay this referral bonus out of pocket as a promotion. Busy wouldn't have "taken the rewards anyway", it's just an out of pocket promotional expense.

Perhaps they fund it with curation payouts from the Busy.org upvote bot? I doubt it has been a large expense yet, as it is newish.