If true this is unfortunate because as more HBD enters the savings accounts there would be no penalty for higher competition. It almost guarantees that we would be constantly pushing HBD up to the haircut, making Hive >> HBD conversions moot and once again destabilizing the peg to both the downside and upside.
Eh we'll figure it out when we get there.
One of the largest sources of inflation in Hive/Steem historically (possibly the largest overall) is the excess inflation created by HBD/SBD conversions while the feed price is low. HBD interest may actually lower inflation overall if it is sufficient to discourage conversions at low prices.
The interest will need to be balanced against the debt burden and rate of conversions. If witnesses can be trusted to be actively involved, they can adjust the HBD interest up or down depending on if we're getting too close to the debt limit, or too much conversions etc.
Very good point, HBD is not pegged by fiat but algorithmically by HIVE, it is more like debt, leading to increased inflation during a bear market, to maintain the peg, more HIVE need to be created through the conversion function. While many users believed that the inflation of STEEM was below 10%, it was actually above 20% p.a. in the bear market because of the SBD debt, which was devastating especially in a bear market. Without the haircut rule that limits the amount of HBD and the conversion rate, HIVE would get hyperinflated during a bear market.