The entire idea here is to align making more money with content discovery and making it more expensive to behave in a way that contradicts that (eg self voting or vote selling)

It's not inconceivable that with the right economic incentives, we'll reach a equilibrium of relatively good behavior that'll continue to serve the entire platform well over time. Behavior that deteriorates over time isn't necessarily an inevitable product of stake based voting. It all depends on how well we align individual profit maximization behavior with honest curation.

It's hard to abuse a modest level of free downvotes in the sense of profiting from them. They can be abused in the general sense to bully and harass people, sure, it's one of the downsides. The idea is to limit them as much as possible while still have a sufficient amount of them to turn this place around.