This is in the whitepaper (page 27):
So yes, anyone can earn rewards by posting content, but voters are needed too, and you need many votes per post (on average) to achieve effective curation. High SBD prices tip the balance in the opposite direction, reducing the relative value of voting, since curation rewards are paid in SP.
And yes, if I understand you, I agree with your second point. SBDs were designed with one purpose in mind, to have a stable value. If they're not doing that, then they are failing.
The whitepaper also has 52+ week power downs and exponential whale voting.
The repeated appeals to it are fallacious appeals to authority.
Actually, it doesn't. The copy I pulled that from was rewritten last year to match the current state of the block chain. The link is here - https://steem.io/SteemWhitePaper.pdf
And it says:
And
And even if it had been obsolete, that wouldn't change the thrust of my comment which is that high SBD prices incentivize authors at the expense of voters and other stakeholders in a way that discourages quality content discovery.