Word of mouth is the most effective marketing. Ask any marketer. However, as profiteering discouraged folks that made the effort to come here, the effect of that marketing was to discourage new users by those discouraged relating their complaints about how things were here. That's very effective, just not at bringing new people here, as we see.
All the changes HF21 brings are percentage changes. How do you achieve qualitative evolution with quantitative changes? All the complaints the one million or so users that were chased off had are being increased. I don't believe anyone expects anything different from what's going to happen as a result of making people less welcome here than they were when one million were chased off.
You don't have to bang your head on a brick wall 21 times to realize it hurts, and how to stop hurting yourself.
Free downvotes is brand new and not a percentage change. Some percentage changes can have a qualitatitive effect once thresholds are reached and it tips the system into a new balance point. We'll have to see to what extent that happens or not.
While you are correct to point out that quantitative changes can concatenate to create qualitative changes, free is simply less expensive. TBQH the downvote pool isn't free at all, since it comes at the expense of other benefits that would otherwise be paid from the pool, in exactly the same way that free healthcare, college, or any other welfare proposal isn't free.
However, I do believe it will result in qualitative changes. I foresee the development of a market for downvotes, and this will have an extremely negative impact on Steem society, as have all other automated voting mechanisms.
We will indeed see what comes of it.
That is a bad analogy. Free downvotes do not cost or expend any significant resources, unlike healthcare, college, etc.