On chain HIVE to HBD conversions are a good thing. It doesn't really remove "value" from the system as a whole. For one, assuming the HBD is just held in savings, the HIVE is not causing selling pressure on the spot markets.

The only potential downside is too many people doing this and potentially losing the dollar peg of HBD if we have a drastic drawdown in the price of HIVE. There is a large buffer currently, and I think that threshold is also set to increase in subsequent hardforks.