There's a reason it wasn't pegged well in the past: it was only pegged in one direction. That is no longer true, and from my perspective, the peg works really well now.
The farthest it has moved from the peg since the last peg improvement was about 1.20, which is not too bad in my opinion (we've seen fluctuations that high between between Euro and USD).
Also even that 1.20 fluctuation could have been easily squashed by stakeholders, but it was just so profitable to stakeholders and the DHF that no stakeholder really wanted to do it. It was probably a once-in-a-lifetime chance to make some bank for the DHF and most of the big traders involved understood the situation well enough to keep their profits at a reasonable level in order to keep the profit train going. I think none of us were too concerned about keeping the peg that tight at that time, because there just weren't a lot of commercial uses of HBD at that point that would be disrupted by the slight rise in the price of HBD.
But I don't think we're likely to see that situation repeat again (although it would be nice if it did, assuming commerce use hasn't picked up by then) as I suspect that whoever tried to push the price up learned an important lesson about how strong the new pegging mechanism is, even though it is decentralized in nature.
We have an extremely forceful mechanism for driving the price down to 1.05 via the HBD conversion operation. For tighter pegging beyond that point, the DHF can do the rest, as it grows in size and the hbd stabilizer gains trading power. I believe that eventually sentiment combined with hard lessons to traders who try to break the peg will keep it pretty much at $1 on the upside (well, probably a little more that $1 if more external traders become aware of the interest rate they can receive for holding it, in which case witnesses should be able to impact the price some by updates to the interest rate).
If you look at the low side of the peg, it doesn't tend to go below 0.90 and usually hangs around 0.95 to 1.00. Again that slight variation is just a source of profit for stakeholders and the DHF, who can buy it up at below $1 price, then convert it to $1 worth of Hive. This cycle acts as a decent incentive for stakeholders to support the price and profit from their virtuous behavior :-)
As the trading volume for HBD increases, I expect the trading range around the peg to narrow, because traders will be able to profit more from smaller spreads between the trading price and the conversion price when they can make more trades (less profit per trade but they can make it up in volume, so there will be more price competition among traders).
One final factor that will improve the lower side of the peg is the change we're making in this upcoming hardfork to allow the HBD supply to increase. This will reduce the chance for a haircut, which is probably the main threat to sustaining HBD at the value of $1 right now (it's not a high risk even now, but the more headroom the better).
So, basically I think the peg rules are "good enough". We could tweak it more, but I think it is better to wait and see if the peg continues to hold well enough with current rules.
I personally think the slight variation around the peg is a strong favorable point for HBD, since it makes it hard to attack via the regulatory rules that seem likely to be aimed at most stablecoins soon.
Thanks for taking the time to thoroughly explain this.