just happens to be following Steem which happens to be near $1.

Here is an interesting chart to test the hypothesis of SBD being linked with STEEM.

https://www.tradingview.com/symbols/spread/BITTREX%3ASTEEMBTC%2FBITTREX%3ASBDBTC/

In fact, there isn't that strong of a link. The ratio has varied from 0.2 in December (SBD worth 5x more than STEEM) to a high of about 1.6 in mid May (SBD worth only 62% as much as STEEM) before reversing and heading back down. What happened in mid May to cause such a clear and rapid reversal after an 8x increase?

Well that was exactly when the the debt ratio reached 2% and SBD printing started getting reduced (and STEEM printing increased)! This had precisely the effect one would expect from the change in supply (though not what one would normally want): SBD got relatively stronger and STEEM got relatively weaker.

The improvements made in HF20 (mostly increasing the 2-5% threshold to 9-10% instead) should be very helpful, although it still may not be enough. It's a step in the right direction for sure.