If 20% is currently sustainable, then I think it should stay at 20%. Why not? If signs start to suggest it isn't sustainable then let's reduce it. There does need to be a lot of HBD if we ever hope to have it widely used as a stablecoin.

If HBD interest IS reduced, I think it should be more gradual.

I think reducing post and curation rewards disincentivizes those things, and I'm not sure that is a good idea. The Hive blockchain needs more participation and I think rewarding posting and curating encourages that better than interest on stake. A slight shift could be ok though.

In addition to reasons already mentioned for buying/holding hive, it also has a vastly larger potential upside than HBD. Its value could easily rise 100% or more. Thats better than 20%.